title: Optics

text: All of the results from geometrical optics can be recovered using the techniques of Fourier optics which apply many of the same mathematical and analytical techniques used in acoustic engineering and signal processing.


title: Optics

text: Gaussian beam propagation is a simple paraxial physical optics model for the propagation of coherent radiation such as laser beams. This technique partially accounts for diffraction, allowing accurate calculations of the rate at which a laser beam expands with distance, and the minimum size to which the beam can be focused. Gaussian beam propagation thus bridges the gap between geometric and physical optics.


title: Optics

text: In the absence of nonlinear effects, the superposition principle can be used to predict the shape of interacting waveforms through the simple addition of the disturbances. This interaction of waves to produce a resulting pattern is generally termed "interference" and can result in a variety of outcomes. If two waves of the same wavelength and frequency are "in phase", both the wave crests and wave troughs align. This results in constructive interference and an increase in the amplitude of the wave, which for light is associated with a brightening of the waveform in that location. Alternatively, if the two waves of the same wavelength and frequency are out of phase, then the wave crests will align with wave troughs and vice versa. This results in destructive interference and a decrease in the amplitude of the wave, which for light is associated with a dimming of the waveform at that location. See below for an illustration of this effect.


title: Optics

text: Since the Huygens–Fresnel principle states that every point of a wavefront is associated with the production of a new disturbance, it is possible for a wavefront to interfere with itself constructively or destructively at different locations producing bright and dark fringes in regular and predictable patterns. Interferometry is the science of measuring these patterns, usually as a means of making precise determinations of distances or angular resolutions. The Michelson interferometer was a famous instrument which used interference effects to accurately measure the speed of light.


title: Optics

text: The appearance of thin films and coatings is directly affected by interference effects. Antireflective coatings use destructive interference to reduce the reflectivity of the surfaces they coat, and can be used to minimise glare and unwanted reflections. The simplest case is a single layer with a thickness of one-fourth the wavelength of incident light. The reflected wave from the top of the film and the reflected wave from the film/material interface are then exactly 180° out of phase, causing destructive interference. The waves are only exactly out of phase for one wavelength, which would typically be chosen to be near the centre of the visible spectrum, around 550 nm. More complex designs using multiple layers can achieve low reflectivity over a broad band, or extremely low reflectivity at a single wavelength.


title: Optics

text: Constructive interference in thin films can create a strong reflection of light in a range of wavelengths, which can be narrow or broad depending on the design of the coating. These films are used to make dielectric mirrors, interference filters, heat reflectors, and filters for colour separation in colour television cameras. This interference effect is also what causes the colourful rainbow patterns seen in oil slicks.


title: Optics

text: Diffraction is the process by which light interference is most commonly observed. The effect was first described in 1665 by Francesco Maria Grimaldi, who also coined the term from the Latin "diffringere", 'to break into pieces'. Later that century, Robert Hooke and Isaac Newton also described phenomena now known to be diffraction in Newton's rings while James Gregory recorded his observations of diffraction patterns from bird feathers.


title: Optics

text: The first physical optics model of diffraction that relied on the Huygens–Fresnel principle was developed in 1803 by Thomas Young in his interference experiments with the interference patterns of two closely spaced slits. Young showed that his results could only be explained if the two slits acted as two unique sources of waves rather than corpuscles. In 1815 and 1818, Augustin-Jean Fresnel firmly established the mathematics of how wave interference can account for diffraction.


title: Optics

text: The simplest physical models of diffraction use equations that describe the angular separation of light and dark fringes due to light of a particular wavelength (λ). In general, the equation takes the form


title: Optics

text: where formula_15 is the separation between two wavefront sources (in the case of Young's experiments, it was two slits), formula_16 is the angular separation between the central fringe and the formula_17th order fringe, where the central maximum is formula_18.


title: Optics

text: This equation is modified slightly to take into account a variety of situations such as diffraction through a single gap, diffraction through multiple slits, or diffraction through a diffraction grating that contains a large number of slits at equal spacing. More complicated models of diffraction require working with the mathematics of Fresnel or Fraunhofer diffraction.


title: Optics

text: X-ray diffraction makes use of the fact that atoms in a crystal have regular spacing at distances that are on the order of one angstrom. To see diffraction patterns, x-rays with similar wavelengths to that spacing are passed through the crystal. Since crystals are three-dimensional objects rather than two-dimensional gratings, the associated diffraction pattern varies in two directions according to Bragg reflection, with the associated bright spots occurring in unique patterns and formula_15 being twice the spacing between atoms.


title: Optics

text: Diffraction effects limit the ability of an optical detector to optically resolve separate light sources. In general, light that is passing through an aperture will experience diffraction and the best images that can be created (as described in diffraction-limited optics) appear as a central spot with surrounding bright rings, separated by dark nulls; this pattern is known as an Airy pattern, and the central bright lobe as an Airy disk. The size of such a disk is given by


title: Optics

text: where "θ" is the angular resolution, "λ" is the wavelength of the light, and "D" is the diameter of the lens aperture. If the angular separation of the two points is significantly less than the Airy disk angular radius, then the two points cannot be resolved in the image, but if their angular separation is much greater than this, distinct images of the two points are formed and they can therefore be resolved. Rayleigh defined the somewhat arbitrary "Rayleigh criterion" that two points whose angular separation is equal to the Airy disk radius (measured to first null, that is, to the first place where no light is seen) can be considered to be resolved. It can be seen that the greater the diameter of the lens or its aperture, the finer the resolution. Interferometry, with its ability to mimic extremely large baseline apertures, allows for the greatest angular resolution possible.


title: Optics

text: For astronomical imaging, the atmosphere prevents optimal resolution from being achieved in the visible spectrum due to the atmospheric scattering and dispersion which cause stars to twinkle. Astronomers refer to this effect as the quality of astronomical seeing. Techniques known as adaptive optics have been used to eliminate the atmospheric disruption of images and achieve results that approach the diffraction limit.


title: Optics

text: Refractive processes take place in the physical optics limit, where the wavelength of light is similar to other distances, as a kind of scattering. The simplest type of scattering is Thomson scattering which occurs when electromagnetic waves are deflected by single particles. In the limit of Thomson scattering, in which the wavelike nature of light is evident, light is dispersed independent of the frequency, in contrast to Compton scattering which is frequency-dependent and strictly a quantum mechanical process, involving the nature of light as particles. In a statistical sense, elastic scattering of light by numerous particles much smaller than the wavelength of the light is a process known as Rayleigh scattering while the similar process for scattering by particles that are similar or larger in wavelength is known as Mie scattering with the Tyndall effect being a commonly observed result. A small proportion of light scattering from atoms or molecules may undergo Raman scattering, wherein the frequency changes due to excitation of the atoms and molecules. Brillouin scattering occurs when the frequency of light changes due to local changes with time and movements of a dense material.


title: Optics

text: Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties ("material dispersion") or to the geometry of an optical waveguide ("waveguide dispersion"). The most familiar form of dispersion is a decrease in index of refraction with increasing wavelength, which is seen in most transparent materials. This is called "normal dispersion". It occurs in all dielectric materials, in wavelength ranges where the material does not absorb light. In wavelength ranges where a medium has significant absorption, the index of refraction can increase with wavelength. This is called "anomalous dispersion".


title: Optics

text: The separation of colours by a prism is an example of normal dispersion. At the surfaces of the prism, Snell's law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin(sin (θ) / "n"). Thus, blue light, with its higher refractive index, is bent more strongly than red light, resulting in the well-known rainbow pattern.


title: Optics

text: Material dispersion is often characterised by the Abbe number, which gives a simple measure of dispersion based on the index of refraction at three specific wavelengths. Waveguide dispersion is dependent on the propagation constant. Both kinds of dispersion cause changes in the group characteristics of the wave, the features of the wave packet that change with the same frequency as the amplitude of the electromagnetic wave. "Group velocity dispersion" manifests as a spreading-out of the signal "envelope" of the radiation and can be quantified with a group dispersion delay parameter:


title: Optics

text: where "n" is the index of refraction and "c" is the speed of light in a vacuum. This gives a simpler form for the dispersion delay parameter:


title: Optics

text: If "D" is less than zero, the medium is said to have "positive dispersion" or normal dispersion. If "D" is greater than zero, the medium has "negative dispersion". If a light pulse is propagated through a normally dispersive medium, the result is the higher frequency components slow down more than the lower frequency components. The pulse therefore becomes "positively chirped", or "up-chirped", increasing in frequency with time. This causes the spectrum coming out of a prism to appear with red light the least refracted and blue/violet light the most refracted. Conversely, if a pulse travels through an anomalously (negatively) dispersive medium, high-frequency components travel faster than the lower ones, and the pulse becomes "negatively chirped", or "down-chirped", decreasing in frequency with time.


title: Optics

text: The result of group velocity dispersion, whether negative or positive, is ultimately temporal spreading of the pulse. This makes dispersion management extremely important in optical communications systems based on optical fibres, since if dispersion is too high, a group of pulses representing information will each spread in time and merge, making it impossible to extract the signal.


title: Optics

text: Polarization is a general property of waves that describes the orientation of their oscillations. For transverse waves such as many electromagnetic waves, it describes the orientation of the oscillations in the plane perpendicular to the wave's direction of travel. The oscillations may be oriented in a single direction (linear polarization), or the oscillation direction may rotate as the wave travels (circular or elliptical polarization). Circularly polarised waves can rotate rightward or leftward in the direction of travel, and which of those two rotations is present in a wave is called the wave's chirality.


title: Optics

text: The typical way to consider polarization is to keep track of the orientation of the electric field vector as the electromagnetic wave propagates. The electric field vector of a plane wave may be arbitrarily divided into two perpendicular components labeled "x" and "y" (with z indicating the direction of travel). The shape traced out in the x-y plane by the electric field vector is a Lissajous figure that describes the "polarization state". The following figures show some examples of the evolution of the electric field vector (blue), with time (the vertical axes), at a particular point in space, along with its "x" and "y" components (red/left and green/right), and the path traced by the vector in the plane (purple): The same evolution would occur when looking at the electric field at a particular time while evolving the point in space, along the direction opposite to propagation.


title: Optics

text: In the leftmost figure above, the x and y components of the light wave are in phase. In this case, the ratio of their strengths is constant, so the direction of the electric vector (the vector sum of these two components) is constant. Since the tip of the vector traces out a single line in the plane, this special case is called linear polarization. The direction of this line depends on the relative amplitudes of the two components.


title: Optics

text: In the middle figure, the two orthogonal components have the same amplitudes and are 90° out of phase. In this case, one component is zero when the other component is at maximum or minimum amplitude. There are two possible phase relationships that satisfy this requirement: the "x" component can be 90° ahead of the "y" component or it can be 90° behind the "y" component. In this special case, the electric vector traces out a circle in the plane, so this polarization is called circular polarization. The rotation direction in the circle depends on which of the two-phase relationships exists and corresponds to "right-hand circular polarization" and "left-hand circular polarization".


title: Optics

text: In all other cases, where the two components either do not have the same amplitudes and/or their phase difference is neither zero nor a multiple of 90°, the polarization is called elliptical polarization because the electric vector traces out an ellipse in the plane (the "polarization ellipse"). This is shown in the above figure on the right. Detailed mathematics of polarization is done using Jones calculus and is characterised by the Stokes parameters.


title: Optics

text: Media that have different indexes of refraction for different polarization modes are called "birefringent". Well known manifestations of this effect appear in optical wave plates/retarders (linear modes) and in Faraday rotation/optical rotation (circular modes). If the path length in the birefringent medium is sufficient, plane waves will exit the material with a significantly different propagation direction, due to refraction. For example, this is the case with macroscopic crystals of calcite, which present the viewer with two offset, orthogonally polarised images of whatever is viewed through them. It was this effect that provided the first discovery of polarization, by Erasmus Bartholinus in 1669. In addition, the phase shift, and thus the change in polarization state, is usually frequency dependent, which, in combination with dichroism, often gives rise to bright colours and rainbow-like effects. In mineralogy, such properties, known as pleochroism, are frequently exploited for the purpose of identifying minerals using polarization microscopes. Additionally, many plastics that are not normally birefringent will become so when subject to mechanical stress, a phenomenon which is the basis of photoelasticity. Non-birefringent methods, to rotate the linear polarization of light beams, include the use of prismatic polarization rotators which use total internal reflection in a prism set designed for efficient collinear transmission.


title: Optics

text: Media that reduce the amplitude of certain polarization modes are called "dichroic", with devices that block nearly all of the radiation in one mode known as "polarizing filters" or simply "polarisers". Malus' law, which is named after Étienne-Louis Malus, says that when a perfect polariser is placed in a linear polarised beam of light, the intensity, "I", of the light that passes through is given by


title: Optics

text: A beam of unpolarised light can be thought of as containing a uniform mixture of linear polarizations at all possible angles. Since the average value of formula_26 is 1/2, the transmission coefficient becomes


title: Optics

text: In practice, some light is lost in the polariser and the actual transmission of unpolarised light will be somewhat lower than this, around 38% for Polaroid-type polarisers but considerably higher (>49.9%) for some birefringent prism types.


title: Optics

text: In addition to birefringence and dichroism in extended media, polarization effects can also occur at the (reflective) interface between two materials of different refractive index. These effects are treated by the Fresnel equations. Part of the wave is transmitted and part is reflected, with the ratio depending on the angle of incidence and the angle of refraction. In this way, physical optics recovers Brewster's angle. When light reflects from a thin film on a surface, interference between the reflections from the film's surfaces can produce polarization in the reflected and transmitted light.


title: Optics

text: Most sources of electromagnetic radiation contain a large number of atoms or molecules that emit light. The orientation of the electric fields produced by these emitters may not be correlated, in which case the light is said to be "unpolarised". If there is partial correlation between the emitters, the light is "partially polarised". If the polarization is consistent across the spectrum of the source, partially polarised light can be described as a superposition of a completely unpolarised component, and a completely polarised one. One may then describe the light in terms of the degree of polarization, and the parameters of the polarization ellipse.


title: Optics

text: Light reflected by shiny transparent materials is partly or fully polarised, except when the light is normal (perpendicular) to the surface. It was this effect that allowed the mathematician Étienne-Louis Malus to make the measurements that allowed for his development of the first mathematical models for polarised light. Polarization occurs when light is scattered in the atmosphere. The scattered light produces the brightness and colour in clear skies. This partial polarization of scattered light can be taken advantage of using polarizing filters to darken the sky in photographs. Optical polarization is principally of importance in chemistry due to circular dichroism and optical rotation (""circular birefringence"") exhibited by optically active (chiral) molecules.


title: Optics

text: "Modern optics" encompasses the areas of optical science and engineering that became popular in the 20th century. These areas of optical science typically relate to the electromagnetic or quantum properties of light but do include other topics. A major subfield of modern optics, quantum optics, deals with specifically quantum mechanical properties of light. Quantum optics is not just theoretical; some modern devices, such as lasers, have principles of operation that depend on quantum mechanics. Light detectors, such as photomultipliers and channeltrons, respond to individual photons. Electronic image sensors, such as CCDs, exhibit shot noise corresponding to the statistics of individual photon events. Light-emitting diodes and photovoltaic cells, too, cannot be understood without quantum mechanics. In the study of these devices, quantum optics often overlaps with quantum electronics.


title: Optics

text: Specialty areas of optics research include the study of how light interacts with specific materials as in crystal optics and metamaterials. Other research focuses on the phenomenology of electromagnetic waves as in singular optics, non-imaging optics, non-linear optics, statistical optics, and radiometry. Additionally, computer engineers have taken an interest in integrated optics, machine vision, and photonic computing as possible components of the "next generation" of computers.


title: Optics

text: Today, the pure science of optics is called optical science or optical physics to distinguish it from applied optical sciences, which are referred to as optical engineering. Prominent subfields of optical engineering include illumination engineering, photonics, and optoelectronics with practical applications like lens design, fabrication and testing of optical components, and image processing. Some of these fields overlap, with nebulous boundaries between the subjects' terms that mean slightly different things in different parts of the world and in different areas of industry. A professional community of researchers in nonlinear optics has developed in the last several decades due to advances in laser technology.


title: Optics

text: A laser is a device that emits light, a kind of electromagnetic radiation, through a process called "stimulated emission". The term "laser" is an acronym for "Light Amplification by Stimulated Emission of Radiation". Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses. Because the microwave equivalent of the laser, the "maser", was developed first, devices that emit microwave and radio frequencies are usually called "masers".


title: Optics

text: The first working laser was demonstrated on 16 May 1960 by Theodore Maiman at Hughes Research Laboratories. When first invented, they were called "a solution looking for a problem". Since then, lasers have become a multibillion-dollar industry, finding utility in thousands of highly varied applications. The first application of lasers visible in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974. The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser, but the compact disc player was the first laser-equipped device to become truly common in consumers' homes, beginning in 1982. These optical storage devices use a semiconductor laser less than a millimetre wide to scan the surface of the disc for data retrieval. Fibre-optic communication relies on lasers to transmit large amounts of information at the speed of light. Other common applications of lasers include laser printers and laser pointers. Lasers are used in medicine in areas such as bloodless surgery, laser eye surgery, and laser capture microdissection and in military applications such as missile defence systems, electro-optical countermeasures (EOCM), and lidar. Lasers are also used in holograms, bubblegrams, laser light shows, and laser hair removal.


title: Optics

text: The Kapitsa–Dirac effect causes beams of particles to diffract as the result of meeting a standing wave of light. Light can be used to position matter using various phenomena (see optical tweezers).


title: Optics

text: Optics is part of everyday life. The ubiquity of visual systems in biology indicates the central role optics plays as the science of one of the five senses. Many people benefit from eyeglasses or contact lenses, and optics are integral to the functioning of many consumer goods including cameras. Rainbows and mirages are examples of optical phenomena. Optical communication provides the backbone for both the Internet and modern telephony.


title: Optics

text: The human eye functions by focusing light onto a layer of photoreceptor cells called the retina, which forms the inner lining of the back of the eye. The focusing is accomplished by a series of transparent media. Light entering the eye passes first through the cornea, which provides much of the eye's optical power. The light then continues through the fluid just behind the cornea—the anterior chamber, then passes through the pupil. The light then passes through the lens, which focuses the light further and allows adjustment of focus. The light then passes through the main body of fluid in the eye—the vitreous humour, and reaches the retina. The cells in the retina line the back of the eye, except for where the optic nerve exits; this results in a blind spot.


title: Optics

text: There are two types of photoreceptor cells, rods and cones, which are sensitive to different aspects of light. Rod cells are sensitive to the intensity of light over a wide frequency range, thus are responsible for black-and-white vision. Rod cells are not present on the fovea, the area of the retina responsible for central vision, and are not as responsive as cone cells to spatial and temporal changes in light. There are, however, twenty times more rod cells than cone cells in the retina because the rod cells are present across a wider area. Because of their wider distribution, rods are responsible for peripheral vision.


title: Optics

text: In contrast, cone cells are less sensitive to the overall intensity of light, but come in three varieties that are sensitive to different frequency-ranges and thus are used in the perception of colour and photopic vision. Cone cells are highly concentrated in the fovea and have a high visual acuity meaning that they are better at spatial resolution than rod cells. Since cone cells are not as sensitive to dim light as rod cells, most night vision is limited to rod cells. Likewise, since cone cells are in the fovea, central vision (including the vision needed to do most reading, fine detail work such as sewing, or careful examination of objects) is done by cone cells.


title: Optics

text: Ciliary muscles around the lens allow the eye's focus to be adjusted. This process is known as accommodation. The near point and far point define the nearest and farthest distances from the eye at which an object can be brought into sharp focus. For a person with normal vision, the far point is located at infinity. The near point's location depends on how much the muscles can increase the curvature of the lens, and how inflexible the lens has become with age. Optometrists, ophthalmologists, and opticians usually consider an appropriate near point to be closer than normal reading distance—approximately 25 cm.


title: Optics

text: Defects in vision can be explained using optical principles. As people age, the lens becomes less flexible and the near point recedes from the eye, a condition known as presbyopia. Similarly, people suffering from hyperopia cannot decrease the focal length of their lens enough to allow for nearby objects to be imaged on their retina. Conversely, people who cannot increase the focal length of their lens enough to allow for distant objects to be imaged on the retina suffer from myopia and have a far point that is considerably closer than infinity. A condition known as astigmatism results when the cornea is not spherical but instead is more curved in one direction. This causes horizontally extended objects to be focused on different parts of the retina than vertically extended objects, and results in distorted images.


title: Optics

text: All of these conditions can be corrected using corrective lenses. For presbyopia and hyperopia, a converging lens provides the extra curvature necessary to bring the near point closer to the eye while for myopia a diverging lens provides the curvature necessary to send the far point to infinity. Astigmatism is corrected with a cylindrical surface lens that curves more strongly in one direction than in another, compensating for the non-uniformity of the cornea.


title: Optics

text: The optical power of corrective lenses is measured in diopters, a value equal to the reciprocal of the focal length measured in metres; with a positive focal length corresponding to a converging lens and a negative focal length corresponding to a diverging lens. For lenses that correct for astigmatism as well, three numbers are given: one for the spherical power, one for the cylindrical power, and one for the angle of orientation of the astigmatism.


title: Optics

text: Optical illusions (also called visual illusions) are characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that differs from the object being imaged. Optical illusions can be the result of a variety of phenomena including physical effects that create images that are different from the objects that make them, the physiological effects on the eyes and brain of excessive stimulation (e.g. brightness, tilt, colour, movement), and cognitive illusions where the eye and brain make unconscious inferences.


title: Optics

text: Cognitive illusions include some which result from the unconscious misapplication of certain optical principles. For example, the Ames room, Hering, Müller-Lyer, Orbison, Ponzo, Sander, and Wundt illusions all rely on the suggestion of the appearance of distance by using converging and diverging lines, in the same way that parallel light rays (or indeed any set of parallel lines) appear to converge at a vanishing point at infinity in two-dimensionally rendered images with artistic perspective. This suggestion is also responsible for the famous moon illusion where the moon, despite having essentially the same angular size, appears much larger near the horizon than it does at zenith. This illusion so confounded Ptolemy that he incorrectly attributed it to atmospheric refraction when he described it in his treatise, "Optics".


title: Optics

text: Another type of optical illusion exploits broken patterns to trick the mind into perceiving symmetries or asymmetries that are not present. Examples include the café wall, Ehrenstein, Fraser spiral, Poggendorff, and Zöllner illusions. Related, but not strictly illusions, are patterns that occur due to the superimposition of periodic structures. For example, transparent tissues with a grid structure produce shapes known as moiré patterns, while the superimposition of periodic transparent patterns comprising parallel opaque lines or curves produces line moiré patterns.


title: Optics

text: Single lenses have a variety of applications including photographic lenses, corrective lenses, and magnifying glasses while single mirrors are used in parabolic reflectors and rear-view mirrors. Combining a number of mirrors, prisms, and lenses produces compound optical instruments which have practical uses. For example, a periscope is simply two plane mirrors aligned to allow for viewing around obstructions. The most famous compound optical instruments in science are the microscope and the telescope which were both invented by the Dutch in the late 16th century.


title: Optics

text: Microscopes were first developed with just two lenses: an objective lens and an eyepiece. The objective lens is essentially a magnifying glass and was designed with a very small focal length while the eyepiece generally has a longer focal length. This has the effect of producing magnified images of close objects. Generally, an additional source of illumination is used since magnified images are dimmer due to the conservation of energy and the spreading of light rays over a larger surface area. Modern microscopes, known as "compound microscopes" have many lenses in them (typically four) to optimize the functionality and enhance image stability. A slightly different variety of microscope, the comparison microscope, looks at side-by-side images to produce a stereoscopic binocular view that appears three dimensional when used by humans.


title: Optics

text: The first telescopes, called refracting telescopes, were also developed with a single objective and eyepiece lens. In contrast to the microscope, the objective lens of the telescope was designed with a large focal length to avoid optical aberrations. The objective focuses an image of a distant object at its focal point which is adjusted to be at the focal point of an eyepiece of a much smaller focal length. The main goal of a telescope is not necessarily magnification, but rather the collection of light which is determined by the physical size of the objective lens. Thus, telescopes are normally indicated by the diameters of their objectives rather than by the magnification which can be changed by switching eyepieces. Because the magnification of a telescope is equal to the focal length of the objective divided by the focal length of the eyepiece, smaller focal-length eyepieces cause greater magnification.


title: Optics

text: Since crafting large lenses is much more difficult than crafting large mirrors, most modern telescopes are "reflecting telescopes", that is, telescopes that use a primary mirror rather than an objective lens. The same general optical considerations apply to reflecting telescopes that applied to refracting telescopes, namely, the larger the primary mirror, the more light collected, and the magnification is still equal to the focal length of the primary mirror divided by the focal length of the eyepiece. Professional telescopes generally do not have eyepieces and instead place an instrument (often a charge-coupled device) at the focal point instead.


title: Optics

text: The optics of photography involves both lenses and the medium in which the electromagnetic radiation is recorded, whether it be a plate, film, or charge-coupled device. Photographers must consider the reciprocity of the camera and the shot which is summarized by the relation


title: Optics

text: In other words, the smaller the aperture (giving greater depth of focus), the less light coming in, so the length of time has to be increased (leading to possible blurriness if motion occurs). An example of the use of the law of reciprocity is the Sunny 16 rule which gives a rough estimate for the settings needed to estimate the proper exposure in daylight.


title: Optics

text: A camera's aperture is measured by a unitless number called the f-number or f-stop, #, often notated as formula_28, and given by


title: Optics

text: where formula_13 is the focal length, and formula_31 is the diameter of the entrance pupil. By convention, "#" is treated as a single symbol, and specific values of # are written by replacing the number sign with the value. The two ways to increase the f-stop are to either decrease the diameter of the entrance pupil or change to a longer focal length (in the case of a zoom lens, this can be done by simply adjusting the lens). Higher f-numbers also have a larger depth of field due to the lens approaching the limit of a pinhole camera which is able to focus all images perfectly, regardless of distance, but requires very long exposure times.


title: Optics

text: The field of view that the lens will provide changes with the focal length of the lens. There are three basic classifications based on the relationship to the diagonal size of the film or sensor size of the camera to the focal length of the lens:


title: Optics

text: The absolute value for the exposure time required depends on how sensitive to light the medium being used is (measured by the film speed, or, for digital media, by the quantum efficiency). Early photography used media that had very low light sensitivity, and so exposure times had to be long even for very bright shots. As technology has improved, so has the sensitivity through film cameras and digital cameras.


title: Optics

text: Other results from physical and geometrical optics apply to camera optics. For example, the maximum resolution capability of a particular camera set-up is determined by the diffraction limit associated with the pupil size and given, roughly, by the Rayleigh criterion.


title: Optics

text: The unique optical properties of the atmosphere cause a wide range of spectacular optical phenomena. The blue colour of the sky is a direct result of Rayleigh scattering which redirects higher frequency (blue) sunlight back into the field of view of the observer. Because blue light is scattered more easily than red light, the sun takes on a reddish hue when it is observed through a thick atmosphere, as during a sunrise or sunset. Additional particulate matter in the sky can scatter different colours at different angles creating colourful glowing skies at dusk and dawn. Scattering off of ice crystals and other particles in the atmosphere are responsible for halos, afterglows, coronas, rays of sunlight, and sun dogs. The variation in these kinds of phenomena is due to different particle sizes and geometries.


title: Optics

text: Mirages are optical phenomena in which light rays are bent due to thermal variations in the refraction index of air, producing displaced or heavily distorted images of distant objects. Other dramatic optical phenomena associated with this include the Novaya Zemlya effect where the sun appears to rise earlier than predicted with a distorted shape. A spectacular form of refraction occurs with a temperature inversion called the Fata Morgana where objects on the horizon or even beyond the horizon, such as islands, cliffs, ships or icebergs, appear elongated and elevated, like "fairy tale castles".


title: Optics

text: Rainbows are the result of a combination of internal reflection and dispersive refraction of light in raindrops. A single reflection off the backs of an array of raindrops produces a rainbow with an angular size on the sky that ranges from 40° to 42° with red on the outside. Double rainbows are produced by two internal reflections with angular size of 50.5° to 54° with violet on the outside. Because rainbows are seen with the sun 180° away from the centre of the rainbow, rainbows are more prominent the closer the sun is to the horizon.


title: DMZ (miniseries)

text: DMZ is an American dystopian streaming television miniseries created by Roberto Patino, based on the comic book series of the same name by Brian Wood and Riccardo Burchielli, that premiered on HBO Max on March 17, 2022. A portion of the miniseries premiered at SXSW on March 12, 2022.


title: DMZ (miniseries)

text: Alma Ortega, an NYC medic, becomes a symbol of hope in a demilitarized Manhattan Island while trying to find her son, who wandered off instead of sticking with her during their evacuation from Manhattan during the Second American Civil War.


title: DMZ (miniseries)

text: In February 2014, it was announced that Syfy was planning on making a TV series adaptation of the comic with former writers and executive producers Andre Jacquemetton and Maria Jacquemetton, with David Heyman as executive producer for the potential series. On October 1, 2019, it was announced that HBO Max was developing a TV series adaptation of the comic with Ava DuVernay directing the pilot with Roberto Patino writing the pilot and as showrunner the series. It was also announced that DuVernay and Patino would both executive produce under their respective overall deals with Warner Bros. Television.


title: DMZ (miniseries)

text: On November 19, 2020, HBO Max gave "DMZ" a limited series order of four episodes, with Patino set to write all of the episodes. In July 2021, Ernest Dickerson joined the series as an executive producer and directed three episodes. The series premiered on March 17, 2022.


title: DMZ (miniseries)

text: On January 22, 2020, Rosario Dawson was cast as Alma. On February 6, 2020, Benjamin Bratt was cast as Parco Delgado. On February 18, 2020, Freddy Miyares was cast as Skel. Upon the limited series order announcement, Hoon Lee and Jordan Preston Carter joined the main cast. On July 12, 2021, Rutina Wesley, Mamie Gummer, Nora Dunn, and Henry G. Sanders were cast in undisclosed capacities while Venus Ariel, Jade Wu, Rey Gallegos, Agam Darshi, and Juani Feliz were cast as series regulars.


title: DMZ (miniseries)

text: On October 1, 2019, the pilot was scheduled to go into production in early 2020, with filming on the pilot wrapping on March 16, 2020. Filming for the pilot took place in Atlanta. Filming for the rest of the episodes wrapped in 2021.


title: DMZ (miniseries)

text: On review aggregator website Rotten Tomatoes, the limited series holds a 50% approval rating based on 14 critic reviews, with an average rating of 5.9/10. The website's critics consensus reads, ""DMZ" takes an explosive premise and lets it fizzle, although a commanding Benjamin Bratt tries his best to ignite some sparks in this uneven dystopian drama." On Metacritic, the miniseries has a score of 58 out of 100, based on 10 critics, indicating "mixed or average reviews".


title: Section 28

text: was a legislative designation for a series of laws across Britain that prohibited the "promotion of homosexuality" by local authorities. Introduced by Margaret Thatcher's Conservative government, it was in effect from 1988 to 2000 in Scotland and from 1988 to 2003 in England and Wales. It caused many organisations such as lesbian, gay, bisexual and transgender student support groups to close, limit their activities or self-censor.


title: Section 28

text: The law is named after Section 28 of the Local Government Act 1988, which added Section 2A to the Local Government Act 1986. Enacted on 24 May 1988, the amendment stated that a local authority "shall not intentionally promote homosexuality or publish material with the intention of promoting homosexuality" or "promote the teaching in any maintained school of the acceptability of homosexuality as a pretended family relationship". It was repealed on 21 June 2000 in Scotland by the Ethical Standards in Public Life etc. (Scotland) Act 2000, one of the first pieces of legislation enacted by the new Scottish Parliament, and on 18 November 2003 in England and Wales by section 122 of the Local Government Act 2003.


title: Section 28

text: Male homosexuality had been illegal within what is now the United Kingdom for centuries, with laws on sodomy having first been passed as the Buggery Act 1533 by Henry VIII in England. This was later compounded upon by the Criminal Law Amendment Act 1885, which criminalised "gross indecency between males", a further-reaching law that criminalised any homosexual activity between men, where previously only anal sex had been criminalised.


title: Section 28

text: In 1954, the Wolfenden report began its investigation into whether or not homosexuality ought to remain an offence in British law, following the arrest and conviction of a number of high-profile men for homosexual offences, such as Lord Montagu of Beaulieu, Michael Pitt-Rivers, and Alan Turing; by the end of 1954, 1,069 men were in prison for such offences. The report, which was published in 1957, recommended that "homosexual behaviour between consenting adults in private should no longer be a criminal offence", and stated that "homosexuality cannot legitimately be regarded as a disease". Following a further decade of debate, homosexuality was decriminalised for those over the age of 21 in the Sexual Offences Act 1967; however, discrimination against gay men, and gay people in general, continued in the following decades.


title: Section 28

text: Beginning in the 1980s, gay men faced a further challenge, with HIV/AIDS first reported in 1981, and the first recorded victims of the disease being a group of gay men. The disease quickly became associated within the media with gay and bisexual men in particular. Though this association was also made in medical circles at first, it was later understood that it was not gay men alone who contracted, and were at risk of, HIV and AIDS. The association of HIV/AIDS with gay and bisexual men worsened their stigmatisation, and this association correlated with higher levels of sexual prejudice, such as homophobic and biphobic attitudes.


title: Section 28

text: Rising negative sentiments towards homosexuality peaked in 1987, the year before Section 28 was enacted. According to the British Social Attitudes Survey, 75% of the population said that homosexual activity was "always or mostly wrong", with just 11% believing it to be "not wrong at all". Five years prior to the enactment, a similar BSAS poll had found that 61% of Conservative and 67% of Labour voters believed homosexual activity to be "always or mostly wrong".


title: Section 28

text: The law's precursor was the publication in 1979 of LEA Arrangements for the School Curriculum, which required local authorities to publish their curriculum policies. Following the legalisation of homosexuality proposals for Scotland (added as an amendment to what became the Criminal Justice (Scotland) Act 1980 by Labour MP Robin Cook), guidance was published indicating that schools should not teach homosexuality as part of sex education lessons. This was part of a deal to ensure government support for legalisation of homosexuality in Scotland.


title: Section 28

text: This was followed, two years later, by the School Curriculum (25 March 1981), in which the secretaries of state (for Education and Wales) said they had decided to "set out in some detail the approach to the school curriculum which they consider should now be followed in the years ahead". Every local education authority was expected to frame policies for the school curriculum consistent with the government's "recommended approach" (DES 1981a:5) which required teaching of only heterosexual intercourse in schools.


title: Section 28

text: The Greater London Council (GLC) directly started funding LGBT groups, and between 1981 and 1984 grants totalling at least £292,548 were given by the GLC to a variety of small gay groups. Another £751,000 was committed towards the setting up of the "London Lesbian and Gay Community Centre" in Islington. About 10 of the 32 local authorities in London, most prominently Islington and Haringey were also funding gay groups at that time, one report estimating that these boroughs and the GLC together donated more than £600,000 to gay projects and groups during 1984.


title: Section 28

text: In 1983, the "Daily Mail" reported that a copy of a book entitled "Jenny lives with Eric and Martin", portraying a young girl who lives with her father and his male partner, was provided in a school library run by the Labour-controlled Inner London Education Authority. More and more councils began to adopt wide-ranging anti-discrimination policies (particularly Ealing, Haringey, Islington, Camden and Manchester who employed officers to counter homophobia).


title: Section 28

text: The attention to this, and the alliances between LGBT and labour unions (including the National Union of Mineworkers (NUM)) – formed by activist groups such as Lesbians and Gays Support the Miners and Lesbians Against Pit Closures – led to the adoption at the Labour Party Annual Conference in 1985 of a resolution to criminalise discrimination against lesbian, gay and bisexual people. This legislation was supported by block voting from the NUM. In addition, the election to Manchester City Council of Margaret Roff in November 1985 as the UK's first openly lesbian Mayor and the publication of "Changing The World" by the GLC in 1985 all fuelled a heightened public awareness of LGBT rights.


title: Section 28

text: But it was not until 1986 that major controversy arose and widespread protest demonstrations made a major contribution towards the subsequent passing of Section 28.


title: Section 28

text: During the 1987 election campaign, the Conservative Party (under the leadership of Margaret Thatcher) issued attack posters claiming that the Labour Party wanted the book "Young, Gay and Proud" to be read in schools, as well as "Police: Out of School", "The Playbook for Kids about Sex", and "The Milkman's on his Way", which, according to the Monday Club's Jill Knight MP – who introduced Section 28 and later campaigned against same-sex marriage – were being taught to "little children as young as five and six", which contained "brightly coloured pictures of little stick men showed all about homosexuality and how it was done", and "explicitly described homosexual intercourse and, indeed, glorified it, encouraging youngsters to believe that it was better than any other sexual way of life".


title: Section 28

text: A demonstration took place in Manchester led by John Shiers against Section 28 in 1988 with 25,000 people attending. A final factor was the tone taken by activist groups such as the Gay Liberation Front, cited by Jill Knight, who in 1999 spoke about the perceived purpose of Section 28:


title: Section 28

text: As a consequence of the DPP deciding that the Crown Prosecution Service could not prosecute the publishers of the "Playbook for Kids about Sex", and the start of local government spending on support groups for LGBT people, papers and Conservative backbench members of Parliament became concerned that left-wing councils or schools would provide children with pro-homosexual material or commend homosexuality to children, both described by parliamentarians backing the bill as morally wrong but which could be carefully policed by judges in applying a narrow sense to the meaning of the word "promote". In 1986 Lord Halsbury first tabled the Local Government Act 1986 (Amendment) Bill, whose long title was "An act to refrain local authorities from promoting homosexuality", in the House of Lords, drafted for him by Lord Campbell of Alloway. At the time, the incumbent Conservative government considered Halsbury's bill to be too misleading and risky. The bill successfully passed the House of Lords and Conservative MP Dame Jill Knight had the bill pass the first stage in the Commons. However, impeded by the 1987 general election, this Bill, commonly called the Earl of Halsbury's Bill failed. Its provisions were not reintroduced by the government on its re-election.


title: Section 28

text: Instead, on 2 December 1987 in committee, Conservative MP David Wilshire proposed an amendment to the new Local Government Bill, as not yet passed, debated as "Clause 27" and later as "Clause 28", intended to be equivalent to the Earl of Halsbury's Bill. The government agreed to support the tabling of the amendment in exchange for Knight forgoing her place on the Health and Medicines Bill standing committee; the amendment received the support of the Ministers for Local Government, Michael Howard and Michael Portillo. On being tabled, a compromise amendment was introduced by Simon Hughes on 8 December 1987 that was debated in the House on 15 December 1987 and which was defeated by a majority of 87, and the bill was approved on its first Commons debate that day. The bill was read a first time in the Lords two days later.


title: Section 28

text: Lord McIntosh of Haringey took up the mantle of Simon Hughes' amendments in the Lords' second reading, furthered by the Bishop of Manchester, Stanley Booth-Clibborn:


title: Section 28

text: A spectrum of literature across the ages was cited (in support of these compromise amendments) by Lord Peston. Nonetheless the Bill passed second reading in the Lords before going to a whole house committee.


title: Section 28

text: In that debate Lord Boyd-Carpenter cited a book display, and proposals for "gay books" to be present in a children's home and a gay pride week to be permissible in schools by named London councils. However, on questioning, he said, "of course, 'promotion' can be treated in different ways. If the clause becomes law it will be a matter for the courts to interpret in the sensible way in which the courts do interpret the law." The SDP peer Viscount Falkland with Lord Henderson of Brompton proposed another compromise amendment, the so-called "Arts Council" amendment, and remarked "There is a suggestion in the clause that in no way can a homosexual have a loving, caring or responsible relationship".


title: Section 28

text: The narrowing amendment failed by a majority of 55 voting against it; and the Lords voted the clause through the following day by a majority of 80.


title: Section 28

text: Michael Colvin MP thus on 8 March asked whether the minister, Christopher Chope, would discuss with the Association of London Authorities the level of expenditure by local authorities in London on support for gay and lesbian groups to which he replied:


title: Section 28

text: Mr Wilshire added that "there is an awful lot more promotion of homosexuality going on by local government outside classrooms", and the tempering amendments of that day's final debate were defeated by 53 votes.


title: Section 28

text: Section 28 became law on 24 May 1988. The night before, several protests were staged by lesbians, including abseiling into Parliament and an invasion of the BBC1's "Six O'Clock News", during which one woman managed to chain herself to Sue Lawley's desk and was sat on by the newsreader Nicholas Witchell.


title: Section 28

text: After Section 28 was passed, there was some debate as to whether it actually applied in schools or whether it applied only to local authorities. Whilst head teachers and Boards of Governors were specifically exempt, schools and teachers became confused as to what was actually permitted and tended to err on the side of caution.


title: Section 28

text: A National Union of Teachers (NUT) statement remarked that "While Section 28 applies to local authorities and not to schools, many teachers believe, albeit wrongly, that it imposes constraints in respect of the advice and counselling they give to pupils. Professional judgement is therefore influenced by the perceived prospect of prosecution", and that it "limits the ability of local authorities to support schools in respect of learning and educating for equality. The effect of Section 28, therefore, is to inhibit anti discrimination initiatives and make it difficult for schools to prevent or address the serious problems that arise from homophobic bullying".


title: Section 28

text: Similarly, the Department for Education and Science said that "Section 28 does not affect the activities of school governors, nor of teachers ... It will not prevent the objective discussion of homosexuality in the classroom, nor the counselling of pupils concerned about their sexuality", to which Knight responded by saying that "This has got to be a mistake. The major point of it was to protect children in schools from having homosexuality thrust upon them". In response to these criticisms, supporters of the bill claimed that the NUT and Department of Education were mistaken, and the section did affect schools.


title: Section 28

text: Some local authorities continued to deliver training to their staff in their education system on how to deliver their services without discrimination against gay people; Manchester City Council continued to sustain four officer posts directly involved in policy making and implementation, contributing to the 1992 report "Section 28 of the Local Government Act 1988: a Guide for Workers in the Education Service, produced by Manchester City Council, May 1992".


title: Section 28

text: Before its repeal, the influence of Section 28 had already been diminished: sex education in England and Wales has been regulated solely by the Secretary of State for Education since the Learning and Skills Act 2000 and the Education Act 1996. Nevertheless, many campaigners still saw abolishing Section 28 as "a symbolic measure against intolerance", and campaigned for its repeal.


title: Section 28

text: Although there were no successful prosecutions under the law, there were legal attempts to use it to stop the funding of LGBT and HIV/AIDS prevention initiatives.


title: Section 28

text: In May 2000, Glasgow City Council halted funding to LGBT groups as local resident Sheena Strain (with the backing of the Christian Institute) took them to the Court of Session, objecting to her council tax being used for what she viewed as the promotion of homosexuality. In particular she objected to the funding of Project for HIV and Aids Care and Education (PHACE West), which produced and distributed a safe sex guide 'Gay Sex Now', which she considered pornographic. In July of the same year, she dropped the case, having reached agreement that the council would send a covering letter to grant recipients stating "You will not spend these monies for the purpose of promoting homosexuality nor shall they be used for the publication of any material which promotes homosexuality." The council had been intending to defend using the argument that PHACE West's principal activity was preventing the spread of HIV/AIDS, so was not promoting homosexuality. In the meantime the Scottish Parliament had passed the Ethical Standards in Public Life etc. (Scotland) Act 2000, which repealed the law.


title: Section 28

text: The introduction of Section 28 served to galvanise the disparate British gay rights movement into action. The resulting protest saw the rise of now famous groups like Stonewall, started by, amongst other people, Ian McKellen and Michael Cashman, and OutRage!. "Schools Out" was formed in 1974 (as "The Gay Teachers Association") and campaigned against the act, as well as supporting teachers on how to counter homophobia in schools. Many other groups not directly associated with LGBT rights also wanted the legislation removed, such as Gingerbread (a charity for single parents), the Family Planning Association and the Terrence Higgins Trust. Many in the labour movement and trade unions also opposed the legislation.


title: Section 28

text: The issue began to divide the Conservative party, heightening divisions between party modernisers and social conservatives. In 1999, Conservative leader William Hague controversially sacked frontbencher Shaun Woodward for refusing to support the party line for Section 28's retention, prompting pro-gay rights Conservatives, such as Steve Norris, to speak out against the decision. 2000 saw gay Conservative advisor Ivan Massow defect to the Labour Party in response to the Conservative Party's continued support of Section 28. The Secondary Heads Association and NASUWT objected to repealing the legislation, saying that "it would be inappropriate to put parents and governors in charge of each school's sex education policy".


title: Section 28

text: On 7 February 2000, the first attempted legislation to repeal Section 28 was introduced by the Labour Government as part of the Local Government Act 2000, but was defeated by a House of Lords campaign led by Baroness Young. The then Shadow Education Secretary and future Prime Minister of the United Kingdom Theresa May called the defeat "a victory for commonsense".


title: Section 28

text: In the Scottish Parliament, the repeal process was more successful. The Equality Network led the campaign in favour of scrapping Section 28, while various groups campaigned against the repeal. The Scottish millionaire businessman Brian Souter privately funded a postal ballot as part of his Keep the Clause campaign, which he claimed returned 86% support for keeping the clause, from a response from less than one third of the 3.9 million registered Scottish voters. The then Communities Minister, Wendy Alexander MSP, criticised the poll, stating "I think what is significant about today's ballot is that two out of three voters rejected, or binned or simply ignored this glorified opinion poll." Nicola Sturgeon of the SNP responded that the result showed that many Scots were concerned about repeal and said: "That is why the SNP have urged a policy for many months that we believe can provide people with the necessary reassurance, by providing a statutory underpinning to the guidelines, and resolve this difficult debate. We believe that the value of [heterosexual] marriage should be clearly referred to in the guidelines". Gay rights campaigner Peter Tatchell stated that "Brian Souter's support for Section 28 is the moral equivalent of the business-funded campaign to maintain racial segregation in the Deep South of the USA in the 1950s." Tatchell said that Souter's campaign was "hateful" and that it is clear that he was using his vast fortune to try to keep a cruel and "bigoted law" intact.


title: Section 28

text: Despite Souter's efforts, Section 28 was repealed by MSPs as part of the Ethical Standards in Public Life Act on 21 June 2000 with a 99 to 17 majority vote with two abstentions. The 17 votes against were all Conservative MSPs.


title: Section 28

text: Despite the previous reversals of the House of Commons by the House of Lords, backbench MPs introduced a fresh amendment to repeal Section 28 in England and Wales as part of another Local Government Bill in early 2003. In response to a further amendment tabled by Conservative MPs, that would have sent the matter to local referendums throughout the country, Edward Davey said "In a liberal democracy, the need to protect minorities properly sometimes means that protection cannot be achieved through the ballot box and that some things are not appropriate for a vote." After a backlash over the party leadership's attitude to gay rights, the Conservative Party allowed its MPs and peers a free vote on the repeal. The amendment was supported by the government and was passed by the Commons in March, by 368 to 76 (71 of the 76 against were Conservative MPs). With organised opposition in the Lords weakened by the death of Baroness Young, peers finally voted in favour of repeal by 180 to 130 in July.


title: Section 28

text: On 18 September 2003, the Local Government Bill received Royal Assent as the Local Government Act 2003 and Section 28 was finally taken off the statute books. However, Kent County Council decided to create their own version of Section 28 to keep the effect of the now repealed law in their schools. This was replaced on 16 December 2004 with provisions stating that heterosexual marriage and family relationships are the only firm foundations for society, as the statement now says: "We will ensure that sex education values family and marriage as the foundation of a civilised society, and a firm basis for the nurturing of children". This was eventually quashed by the Equality Act 2010.


title: Section 28

text: Section 28 was supported by religious groups such as the Salvation Army, the Christian Institute, Christian Action Research and Education, the Muslim Council of Britain, the Pentecostal British Union (a group of conservative Pentecostal churches) and groups within the Catholic Church and the Church of England. The Conservative Party, despite dissent within its ranks on the issue, whipped its members in support of Section 28 in 2000, but in 2003, after further dissent from within the party, allowed a free vote. In the House of Lords, the campaign against the repeal of Section 28 was led by Baroness Young, who died in 2002. Newspapers that strongly supported Section 28 included "The Daily Mail", "The Sun" and "The Daily Telegraph".


title: Section 28

text: In Scotland, the most visible supporters of Section 28 were Brian Souter and the "Daily Record" newspaper.


title: Section 28

text: The main argument in support of Section 28 was to protect children from "predatory homosexuals" and advocates seeking to "indoctrinate" vulnerable young people into homosexuality. Various other arguments were also used in support of Section 28 which are summarised as follows:


title: Section 28

text: Gay rights advocates, such as Stonewall, OutRage!, "Capital Gay", "The Pink Paper" and the "Gay Times" formed the major opposition to Section 28 and led the campaign for its repeal. Prominent individuals who spoke out for the repeal of Section 28 included Sir Ian McKellen, Michael Cashman, Ivan Massow, Mo Mowlam, Simon Callow, Annette Crosbie, Michael Grade, Jane Horrocks, Michael Mansfield QC, Helen Mirren, Claire Rayner, Ned Sherrin and Alan Moore.


title: Section 28

text: A packed benefit held at the Piccadilly Theatre on 5 June 1988 called "Before the Act" mustered over 60 performers, among them Timothy West, Michael Cashman, Simon Rattle, Paul Eddington, Maureen Lipman, the Medici Quartet, the Pet Shop Boys, Maggie Ford, Sheila Hancock, Jill Bennett, Stephen Fry, Richard Griffiths, Harold Pinter, Joan Plowright, Anthony Sher, Ned Sherrin and Ian McKellen.


title: Section 28

text: A coalition of comic book creators, including Alan Moore, Frank Miller, Robert Crumb, Art Spiegelman, Neil Gaiman, and many others, produced a comic anthology called "AARGH" and raised at least £17,000 to contribute to the fight against the legislation, according to Moore. Boy George wrote a song opposed to Section 28, entitled "No Clause 28". The band Chumbawamba recorded a single entitled "Smash Clause 28! Fight the Alton Bill!" which was an attack on Clause/Section 28 and a benefit for a gay rights group; it also featured 12 pages of hand printed notes relating to gay rights. The legislation was also opposed by some religious groups and leaders, such as Richard Harries, Bishop of Oxford. Newspapers that came out in opposition included "The Guardian", "The Independent" and "The Daily Mirror".


title: Section 28

text: Political parties that were opposed to Section 28 included the Labour Party, the Liberal Democrats and the Green Party. In the House of Lords the campaign for repeal was led by openly gay peer Waheed Alli. Perhaps the most famous act of opposition to Section 28 came when Shaun Woodward, a Conservative MP with a transgender sister, defected from the Conservative Party and his seat and joined the ruling Labour Party in opposition to the Conservatives' continued support of Section 28.


title: Section 28

text: The main point of argument claimed by opponents of Section 28 was the complaint that it discriminated against homosexuals and bisexuals, and hence was an intolerant and unjust law. Various other arguments were also used against Section 28 which are summarised as follows:


title: Section 28

text: Some prominent MPs who supported the bill when it was first introduced have since either expressed regret over their support, changed their stance due to different circumstances which have evolved over time, or have argued that the legislation is no longer necessary.


title: Section 28

text: In an interview with gay magazine "Attitude" at the time of the 2005 general election, Michael Howard, then-Leader of the Conservative Party, commented: "[Section 28] was brought in to deal with what was seen to be a specific problem at the time. The problem was the kind of literature that was being used in some schools and distributed to very young children that was seen to promote homosexuality... I thought, rightly or wrongly, that there was a problem in those days. That problem simply doesn't exist now. Nobody's fussed about those issues any more. It's not a problem, so the law shouldn't be hanging around on the statute book".


title: Section 28

text: In February 2006, then-Conservative Party Chairman Francis Maude told Pinknews.co.uk that the policy, which he had voted for, was wrong and a mistake.


title: Section 28

text: In 2000, one year prior to his election to the House of Commons, Conservative Party member David Cameron repeatedly attacked the Labour Government's plans to abolish Section 28, publicly criticising then-Prime Minister Tony Blair as being "anti-family" and accusing him of wanting the "promotion of homosexuality in schools". At the 2001 general election, Cameron was elected as the Member of Parliament for Witney; he continued to support Section 28, voting against its repeal in 2003. The Labour Government were determined to repeal Section 28, and Cameron voted in favour of a Conservative amendment that retained certain aspects of the clause, which gay rights campaigners described as "Section 28 by the back door". The Conservative amendment was unsuccessful, and Section 28 was repealed by the Labour Government without concession, with Cameron absent for the vote on its eventual repeal.


title: Section 28

text: However, in June 2009, Cameron, then-Leader of the Conservative Party, formally apologised for his party's introduction of the law, stating that it was a mistake and had been offensive to gay people. He restated this belief in January 2010, proposing to alter Conservative Party policy to reflect his belief that equality should be "embedded" in British schools.


title: Section 28

text: In 2012, when the Coalition government launched its consultation into legalising same-sex marriages, Harrow East MP Bob Blackman suggested that David Cameron should resurrect Section 28, stating that he strongly believed that "Section 28 was the right rules to have in school so that we should not promote in any way shape or form promote same-sex relationships" and said he would be "very opposed" to seeing teachers being forced to say same-sex relationships are equivalent to heterosexual relationships. Shortly after, Blackman's Labour predecessor Tony McNulty branded him a "complete idiot" on Twitter.


title: Section 28

text: In 2014, a Stonewall report on homophobic bullying in schools found that 37% of primary school teachers and 29% of secondary school teachers did not know if they were allowed to teach lessons on LGBT+ issues.


title: Section 28

text: In 2015, "Pink News" accused the Evangelical Alliance's report to the Women and Equalities Select Committee's transgender inquiry, which said in part that "children should be protected from having to sort through [questions regarding sex or gender] before they reach an appropriate age" as reminiscent of Section 28.


title: Section 28

text: After the Women and Equalities Select Committee recommended updating the Gender Recognition Act 2004 away from a medicalised approach and towards one based on statutory declarations in 2016, the ensuring and ongoing debate raised fears among some trans people that a new Section 28 could be introduced, especially after equalities minister Liz Truss said that government policy would be based in part on the principle "that the under 18s are protected from decisions that they could make, that are irreversible in the future." LGBT+ rights charity Stonewall stated that the government rhetoric "sounds similar to how young lesbian, gay and bi people were spoken about in the 1980s."


title: Section 28

text: A 2018 study from Anglia Ruskin University found that only 20% of LGBT+ teachers who had taught under Section 28 were openly LGBT+, whereas almost 90% of those had been trained after the repeal of the law were. The study additionally found that 40% of the teachers from the Section 28 era saw their LGBT+ identity as incompatible with their role as teachers, whereas only 13% of the post-Section 28 era teachers did.


title: Section 28

text: Section 28 received renewed attention in late 2011, when Michael Gove, in Clause 28 of the Model Funding Agreement for academies and free schools, added the stipulation that the benefits of marriage be taught in schools. Although the clause does not explicitly mention sexual orientation, with same-sex marriage not being legal at the time, it prompted "The Daily Telegraph" (traditionally supportive of the Conservative Party) to draw comparisons between the two clauses.


title: Section 28

text: Academies and the Department for Education came under greater scrutiny in August 2013, when LGBT activists, in co-ordination with the British Humanist Association (BHA), identified over forty schools whose policies either replicated the language of Section 28 in their sex and relationship education (SRE) policies or were "unhelpfully vague" on the issue. Several of the schools highlighted by the BHA included the Evelyn Grace Academy chain of faith schools – which opened after the repeal of Section 28, Tasker-Milward V.C. School, whose SRE policy, dating from 2008, implied the clause was still in force, and The Northumberland Church of England Academy, who was listed as a School Champion by LGBT rights charity Stonewall and whose staff spoke at Stonewall's 2013 Education for All Conference. In light of the media coverage, the Welsh Government announced an investigation into the Tasker-Milward School, and the Department for Education, announcing its own investigation, stated that schools were prohibited under DfE guidance from discriminating on the basis of sexual orientation.


title: Section 28

text: "Margaret Thatcher Queen of Soho" (2013), a drag comedy musical play, displays what life would have been like if Margaret Thatcher had got lost in Soho on the eve of the vote for Section 28. It was produced in December 2013 by Jon Brittain, Aine Flanagan, Matt Tedford at Theatre503 in London.


title: Section 28

text: "Next Lesson" (2015) is a comedy drama written by Chris Woodley which explores Section 28 in a fictional South East London school from 1988 to 2006. The play was first performed at The Pleasance Theatre, London in 2015. To mark the thirtieth anniversary of Section 28 a new production was staged at Above The Stag Theatre London in August 2018. A staged reading was also performed in The House of Lords by The BRIT School in June 2018.


title: Section 28

text: Russell T. Davies included a scene in the TV series "Queer as Folk" (1999) with a classmate of the gay schoolboy Nathan stopping a teacher discussing an author's sexuality with "You can't teach us about poofs. You're not allowed.". He referenced it again in "It's A Sin" (2021), where gay schoolteacher Ash is ordered to remove books from the school library which reference homosexuality, following the introduction of the law in 1988.


title: HMS Belfast

text: HMS "Belfast" is a Town-class light cruiser that was built for the Royal Navy. She is now permanently moored as a museum ship on the River Thames in London and is operated by the Imperial War Museum.


title: HMS Belfast

text: Construction of "Belfast", the first ship in the Royal Navy to be named after the capital city of Northern Ireland and one of ten Town-class cruisers, began in December 1936. She was launched on St Patrick's Day 1938. Commissioned in early August 1939 shortly before the outbreak of the Second World War, "Belfast" was initially part of the British naval blockade against Germany. In November 1939, "Belfast" struck a German mine and, in spite of fears that she would be scrapped, spent more than two years undergoing extensive repairs. "Belfast" returned to action in November 1942 with improved firepower, radar equipment, and armour. "Belfast" saw action escorting Arctic convoys to the Soviet Union during 1943 and in December 1943 played an important role in the Battle of North Cape, assisting in the destruction of the German warship . In June 1944, "Belfast" took part in Operation Overlord supporting the Normandy landings. In June 1945, she was redeployed to the Far East to join the British Pacific Fleet, arriving shortly before the end of the Second World War. "Belfast" saw further combat action in during the Korean War and underwent an extensive modernisation between 1956 and 1959. A number of further overseas commissions followed before she entered reserve in 1963.


title: HMS Belfast

text: In 1967, efforts were initiated to avert "Belfast" expected scrapping and to preserve her as a museum ship. A joint committee of the Imperial War Museum, the National Maritime Museum, and the Ministry of Defence was established and then reported in June 1968 that preservation was practical. In 1971, however, the government decided against preservation, prompting the formation of the private HMS "Belfast" Trust to campaign for her preservation. The efforts of the Trust were successful, and the government transferred the ship to the Trust in July 1971. Brought to London, she was moored on the River Thames near Tower Bridge in the Pool of London. Opened to the public in October 1971, "Belfast" became a branch of the Imperial War Museum in 1978. A popular tourist attraction, "Belfast" received over 327,000 visitors in 2019. As a branch of a national museum and part of the National Historic Fleet, "Belfast" is supported by the Department for Culture, Media and Sport, admissions income, and the museum's commercial activities.


title: HMS Belfast

text: "Belfast" is a cruiser of the third Town class. The Town class had originated in 1933 as the Admiralty's response to the Imperial Japanese Navy's , an -ton cruiser mounting fifteen guns with a top speed exceeding . The Admiralty's requirement called for a 9,000-ton cruiser, sufficiently armoured to withstand a direct hit from an shell, capable of and mounting twelve 6-inch guns. Seaplanes carried aboard would enable shipping lanes to be patrolled over a wide area, and the class was also to be capable of its own anti-aircraft defence. Under the Director of Naval Construction the new design evolved during 1933. The lead ship of the new class, the 9,100-ton , and her sister , were ordered under the 1933 estimates. Three more cruisers were built to this design, with a further three ships built to a slightly larger 9,400-ton design in 1935–36. By 1935, however, the Admiralty was keen to improve the firepower of these cruisers to match the firepower of the Japanese "Mogami" and American s; both were armed with fifteen 6-inch guns. The Admiralty rejected a design featuring five triple turrets as impractical, while an alternative design fitting four quadruple turrets was rejected as an effective quadruple turret could not be developed. In May 1936 the Admiralty decided to fit triple turrets, whose improved design would permit an increase in deck armour. This modified design became the 10,000-ton "Edinburgh" subclass, named after "Belfast"s sister ship . "Belfast" was ordered from Harland and Wolff on 21 September 1936, and her keel laid on 10 December 1936. Her expected cost was £2,141,514; of which the guns cost £75,000 and the aircraft (two Supermarine Walruses) £66,500. She was launched on Saint Patrick's Day, 17 March 1938, by Anne Chamberlain, the wife of Prime Minister Neville Chamberlain. The launch was filmed by Pathé News. From March to August 1939, "Belfast" was fitted out and underwent sea trials.


title: HMS Belfast

text: When completed, "Belfast" had an overall length of , a beam of and a draught of . Her standard displacement during her sea trials was . She was propelled by four three-drum oil-fired Admiralty water-tube boilers, turning Parsons geared steam turbines, driving four propeller shafts. She was capable of and carried of fuel oil. This gave her a maximum range of at .


title: HMS Belfast

text: "Belfast"s main armament comprised twelve Mk XXIII 6-inch guns in four triple turrets directed by an Admiralty Fire Control Table. With a rate of fire of up to eight rounds per gun per minute, her main battery was capable of a total maximum rate of fire of 96 rounds per minute. Her secondary armament comprised twelve 4-inch guns in six twin mounts. Her initial close-range anti-aircraft armament was sixteen 2-pounder "pom-pom" guns in two eight-barrel mountings, and two quadruple Vickers .50 machine guns. She also mounted six Mk IV 21-inch torpedo tubes in two triple mounts, and fifteen Mk VII depth charges.


title: HMS Belfast

text: "Belfast" was protected by a main armour belt, with deck armour of over her magazines, and over her machinery spaces. Her six-inch turrets were protected by up to of armour.


title: HMS Belfast

text: "Belfast"s aviation capability was provided by two catapult-launched Supermarine Walrus amphibious biplanes. These could be launched from a D1H catapult mounted aft of the forward superstructure, and recovered from the water by two cranes mounted on either side of the forward funnel. The aircraft, operated by the Fleet Air Arm's HMS "Belfast" Flight of 700 Naval Air Squadron, were stowed in two hangars in the forward superstructure.


title: HMS Belfast

text: "Belfast" departed for Portsmouth on 3 August 1939, and was commissioned on 5 August 1939, less than a month before the outbreak of the Second World War. Her first captain was Captain G A Scott with a crew of 761, and her first assignment was to the Home Fleet's 2nd Cruiser Squadron. On 14 August, "Belfast" took part in her first exercise, Operation "Hipper", in which she played the role of a German commerce raider attempting to escape into the Atlantic. By navigating the hazardous Pentland Firth, "Belfast" successfully evaded the Home Fleet.


title: HMS Belfast

text: On 31 August 1939 "Belfast" was transferred to the 18th Cruiser Squadron. Based at Scapa Flow in the Orkney islands, 18th Cruiser Squadron was part of the British effort to impose a naval blockade on Germany. Germany invaded Poland the following day, and Britain and France declared war on 3 September. At 11:40 that morning, "Belfast" received the message ‘Commence hostilities at once against Germany’. On 8 September "Belfast" put to sea from Scapa Flow with the battlecruisers , , her sister ship "Edinburgh" and four destroyers, on a patrol intended to intercept German ships returning from Norway. In particular, they were to search for the Norddeutscher Lloyd liner . No enemy vessels were found. On 25 September, "Belfast" took part in a fleet operation to recover the submarine , during which the ship was attacked by German aircraft, but suffered no damage. On 1 October 1939 "Belfast" left Scapa Flow for a patrol in the North Sea. On 5 October "Belfast" intercepted and boarded a neutral Norwegian factory ship that was sailing in company with six whaling ships. On 8 October the ship sighted the Swedish merchant ship "C. P. Lilljevach" but, in poor weather, did not intercept or board her. The following day she boarded "Tai Yin", a Norwegian ship. "Tai Yin" had been listed by the Admiralty as suspicious, so a prize crew from "Belfast" sailed her to Kirkwall for investigation. On 9 October "Belfast" intercepted a German liner, the 13,615-ton "Cap Norte", north-west of the Faroe Islands. Disguised as a neutral Swedish vessel, SS "Ancona", "Cap Norte" was attempting to return to Germany from Brazil; her passengers included German reservists. Under the Admiralty's prize rules, "Belfast"s crew later received prize money. On 12 October "Belfast" boarded the Swedish ship "Uddeholm", which was also sailed to Kirkwall by a prize crew. Returning to harbour, on the night of 13–14 October, "Belfast" was among the few ships anchored in Scapa Flow, following intelligence reports of an expected air raid. That night, the battleship was torpedoed by German submarine , which had infiltrated the anchorage. On the morning following the sinking, "Belfast" left for Loch Ewe.


title: HMS Belfast

text: On 10 November "Belfast" was taken off the northern patrol and reassigned to the 2nd Cruiser Squadron. This squadron was to form an independent striking force based at Rosyth. On 21 November, "Belfast" was to take part in the force's first sortie, a gunnery exercise. At 10:58 am she detonated a magnetic mine while leaving the Firth of Forth. The mine broke "Belfast"s keel, and wrecked one of her engine and boiler rooms. Twenty officers and men required hospital treatment for injuries caused by the explosion, and a further 26 suffered minor injuries. One man, Painter 2nd Class Henry Stanton, was hospitalised but later died of a head injury, having been thrown against the deckhead by the blast. The tugboat "Krooman", towing gunnery targets for the exercise, released her targets and instead towed "Belfast" to Rosyth for initial repairs.


title: HMS Belfast

text: Initial assessments of "Belfast"s damage showed that, while the mine had done little direct damage to the outer hull, causing only a small hole directly below one of the boiler rooms, the shock of the explosion had caused severe warping, breaking machinery, deforming the decks and causing the keel to hog (bend upwards) by three inches. On 4 January 1940 "Belfast" was decommissioned to Care and Maintenance status, becoming the responsibility of Rosyth Dockyard, and her crew dispersed to other vessels. By 28 June she had been repaired sufficiently to sail to Devonport, arriving on 30 June under the command of Lt Cdr H W Parkinson.


title: HMS Belfast

text: During her repairs, work was carried out to straighten, reconstruct and strengthen her hull. Her armour belt was also extended and thickened. Her armament was updated with newer 2-pounder pom-pom mountings, and her anti-aircraft armament improved with eighteen 20 mm Oerlikon guns in five twin and eight single mountings, replacing two quadruple 0.5-inch Vickers guns. "Belfast" also received new fire control radars for her main, secondary and anti-aircraft guns. Her November 1942 radar fit included one Type 284 set and four Type 283 sets to direct the main armament, three Type 285 sets for the secondary guns, and two Type 282 sets for the 2-pounder anti-aircraft guns. She also received a Type 273 general surface warning radar, Type 251 and 252 sets for identification friend or foe (IFF) purposes, and a Type 281 and Type 242 for air warning. Her 1942 electronics suite also included a Type 270 echosounder. Due to her increased topweight, a bulge was introduced into her hull amidships to improve stability and provide extra longitudinal strength. Her beam had increased to and her draught to forward and aft. Her displacement had risen to  tons.


title: HMS Belfast

text: "Belfast" was recommissioned at Devonport on 3 November 1942, under the command of Captain Frederick Parham. On her return to the Home Fleet "Belfast" was made flagship of the 10th Cruiser Squadron, flying the flag of Rear-Admiral Robert Burnett, who had previously commanded the Home Fleet's destroyer flotillas. The squadron was responsible for the hazardous task of escorting Arctic convoys to the Soviet Union, operating from Scapa Flow and bases in Iceland. Her radar suite reduced "Belfast" need for aerial surveillance, and her aircraft were disembarked in June 1943. "Belfast" spent 1943 engaged on convoy escort and blockade patrol duties, and on 5–6 October of the same year, formed part of the covering force during Operation Leader, an airstrike against German shipping in the waters of northern Norway near Bodø by the aircraft carrier .


title: HMS Belfast

text: On 26 December 1943, "Belfast" participated in the Battle of North Cape. This battle, which occurred during the Arctic night, involved two strong Royal Navy formations; the first, Force One, comprised the cruisers , and "Belfast" (the 10th Cruiser Squadron) with three destroyers, and the second, Force Two, comprised the battleship and the cruiser with four destroyers. On 25 December 1943, Christmas Day, Nazi Germany's left port in northern Norway to attack Convoy JW55B, which was bound for the Soviet Union. The next day Force One encountered "Scharnhorst", prevented her from attacking the convoy, and forced her to retreat after being damaged by the British cruisers. As "Scharnhorst" attacked again at noon she was intercepted by Force Two and sunk by the combined formations. "Belfast" played an important role in the battle; as flagship of the 10th Cruiser Squadron, she was among the first to encounter "Scharnhorst", and coordinated the squadron's defence of the convoy. After "Scharnhorst" turned away from the convoy, Admiral Burnett in "Belfast" shadowed her by radar from outside visual range, enabling her interception by "Duke of York".


title: HMS Belfast

text: After North Cape, "Belfast" refuelled at Kola Inlet before sailing for the United Kingdom, arriving at Scapa to replenish her fuel, ammunition and stores on New Year's Day 1944. "Belfast" sailed to Rosyth on 10 January, where her crew received a period of leave. February 1944 saw "Belfast" resume her Arctic convoy duties, and on 30 March 1944 "Belfast" sailed with the covering force of Operation Tungsten, a large carrier-launched Fleet Air Arm airstrike against the German battleship . Moored in Altafjord in northern Norway, "Tirpitz" was the German navy's last surviving capital ship. Forty-two Fairey Barracuda dive-bombers from and made up the strike force; escorted by eighty fighters. Launched on 3 April, the bombers scored fourteen hits, immobilising "Tirpitz" for two months, with one Barracuda shot down. "Belfast" underwent minor repairs at Rosyth from 23 April to 8 May, while her crew received a period of leave. On 8 May "Belfast" returned to Scapa Flow and carried the King during his pre-invasion visit to the Home Fleet.


title: HMS Belfast

text: For the invasion of Normandy "Belfast" was made headquarters ship of Bombardment Force E flying the flag of Rear-Admiral Frederick Dalrymple-Hamilton, and was to support landings by British and Canadian forces in the Gold and Juno Beach sectors. On 2 June "Belfast" left the River Clyde for her bombardment areas. That morning Prime Minister Winston Churchill had announced his intention to go to sea with the fleet and witness the invasion from HMS "Belfast". This was opposed by the Supreme Allied Commander, General Dwight D. Eisenhower, and the First Sea Lord, Sir Andrew Cunningham. An intervention by the King eventually prevented Churchill from going.


title: HMS Belfast

text: The invasion was to begin on 5 June but bad weather forced a 24-hour delay. At 5:30 am on 6 June, "Belfast" opened fire on a German artillery battery at Ver-sur-Mer, suppressing the guns until the site was overrun by British infantry of 7th Battalion, Green Howards. On 12 June "Belfast" supported Canadian troops moving inland from Juno Beach and returned to Portsmouth on 16 June to replenish her ammunition. She returned two days later for further bombardments. On the night of 6 July "Belfast" was threatened at anchor by German motor torpedo boats ("E-boats"). She evaded them by weighing anchor and moving to the concealment of a smoke screen. "Belfast" fired her last round in anger in European waters on 8 July, in company with the monitor and the battleship , as part of Operation Charnwood. On 10 July she sailed for Scapa, the fighting in France having moved inland beyond the range of her guns. During her five weeks off Normandy, "Belfast" had fired 1,996 rounds from her six-inch guns.


title: HMS Belfast

text: On 29 July 1944, Captain Parham handed over command of HMS "Belfast" to Captain R M Dick, and until April 1945 "Belfast" underwent a refit to prepare for service against Japan in the Far East which improved her accommodation for tropical conditions, and updated her anti-aircraft armament and fire control in order to counter expected kamikaze attacks by Japanese aircraft. By May 1945, "Belfast" mounted thirty-six 2-pounder guns in two eight-gun mounts, four quadruple mounts, and four single mounts. She also mounted fourteen 20 mm Oerlikons. Her two aftmost 4-inch mountings were removed, and the remainder fitted with Remote Power Control. Her empty hangars were converted to crew accommodation, and her aircraft catapult was removed.


title: HMS Belfast

text: Her radar fit now included a Type 277 radar set to replace her Type 273 for surface warning. Her Type 281 air warning set was replaced by a single-antenna Type 281B set, while a Type 293Q was fitted for close-range height-finding and surface warning. A Type 274 set was fitted for main armament fire direction. On 17 June 1945, with the war in Europe at an end, "Belfast" sailed for the Far East via Gibraltar, Malta, Alexandria, Port Said, Aden, Colombo and Sydney. By the time she arrived in Sydney on 7 August "Belfast" had been made flagship of the 2nd Cruiser Squadron of the British Pacific Fleet. While in Sydney "Belfast" underwent another short refit, supplementing her close-range armament with five 40 mm Bofors guns. "Belfast" had been expected to join in Operation Downfall, but this was forestalled by the Japanese surrender on 15 August 1945.


title: HMS Belfast

text: With the end of the war, "Belfast" remained in the Far East, conducting a number of cruises to ports in Japan, China and Malaya and sailing for Portsmouth on 20 August 1947. There she paid off into reserve, and underwent a refit during which her turbines were opened for maintenance. She also received two more single Bofors guns, in place of two of her single 2-pounder mountings. She was recommissioned on 22 September 1948 and, before returning to the Far East, visited her home city of Belfast, arriving on 20 October. The following day, 21 October 1948, the ship's company marked Trafalgar Day with a march through the city. The next day "Belfast" took charge of a silver ship's bell, a gift of the people of Belfast. She sailed for Hong Kong on 23 October to join the Royal Navy's Far East Fleet, arriving in late December. By 1949, the political situation in China was precarious, with the Chinese Civil War moving towards its conclusion. As flagship of the 5th Cruiser Squadron, "Belfast" was the Far Eastern Station's headquarters ship during the April 1949 "Amethyst" Incident, in which a British sloop, , was trapped in the Yangtze River by the communist People's Liberation Army. "Belfast" remained in Hong Kong during 1949, sailing for Singapore on 18 January 1950. There she underwent a minor refit between January to March 1950 and in June she joined the Far East Fleet's summer cruise. On 25 June 1950, while "Belfast" was visiting Hakodate in Japan, North Korean forces crossed the 38th Parallel, starting the Korean War.


title: HMS Belfast

text: With the outbreak of the Korean War, "Belfast" became part of the United Nations naval forces. Originally part of the US Navy's Task Force 77, "Belfast" was detached in order to operate independently on 5 July 1950. During July and early August 1950, "Belfast" undertook coastal patrols and was based at Sasebo in Japan's Nagasaki Prefecture. From 19 July "Belfast" supported troops fighting around Yongdok, accompanied by . That day "Belfast" fired an accurate 350-round bombardment from her 6-inch guns, and was praised by an American admiral as a "straight-shooting ship". On 6 August she sailed for the UK for a short (but needed) refit, after which she again set sail for the far east and arrived back at Sasebo on 31 January 1951.


title: HMS Belfast

text: During 1951 "Belfast" mounted a number of coastal patrols and bombarded a variety of targets. On 1 June she arrived at Singapore for refitting, arriving back on patrol on 31 August. In September 1951 "Belfast" provided anti-aircraft cover for a salvage operation to recover a crashed enemy MiG-15 jet fighter. She conducted further bombardments and patrols before receiving a month's leave from operations, returning to action on 23 December.


title: HMS Belfast

text: In 1952 "Belfast" continued her coastal patrol duties. On 29 July 1952 "Belfast" was hit by enemy fire while engaging an artillery battery on Wolsa-ri island. A 75 mm shell struck a forward compartment, killing a British sailor of Chinese origin in his hammock and wounding four other Chinese ratings. This was the only time "Belfast" was hit by enemy fire during her Korean service. On 27 September 1952 "Belfast" was relieved by two other Town-class cruisers, and HMS "Newcastle", and sailed back to the UK. She had steamed over in the combat zone and fired more than 8,000 rounds from her 6-inch guns during the Korean War. She paid off in Chatham on 4 November 1952 and entered reserve at Devonport on 1 December.


title: HMS Belfast

text: In reserve, "Belfast"s future was uncertain: post-war defence cuts made manpower-intensive cruisers excessively costly to operate, and it was not until March 1955 that the decision was taken to modernise "Belfast". Work began on 6 January 1956. Although described as only an extended refit, the cost of £5.5 million was substantial for this large middle-aged cruiser. Changes included: providing the new twin MK 5 40 mm and the twin 4-inch mount with individual MRS8 directors; the 4-inch guns training and elevation speed was increased to 20 degrees a second; and protecting key parts of the ship against nuclear, biological or chemical attack. This last consideration meant significantly enlarging and enclosing her bridge, creating a two-tiered, five-sided superstructure which radically altered her appearance. The most significant change was better accommodations for a smaller crew more fitting of post-war needs, her tripod masts replaced with lattice masts, and timber decking replaced with steel everywhere except the quarterdeck. The overall effect was to create a cruiser significantly more habitable but different internally and to a degree in external appearance, from wartime cruisers but still essentially a surface warfare, 'anti Sverdlov' cruiser, with anti-aircraft defence, updated only for point defence, with 262 radar, locking only out. "Belfast" recommissioned at Devonport on 12 May 1959. Her close-range armament was standardised to six twin Bofors guns, and her close-range fire direction similarly standardised to eight close-range blind fire directors fitted with Type 262 radar. Her 1959 radar fit included two Type 274, lock and follow radar directors, for main armament direction, against sea and land targets, (other 1950s cruiser reconstructions of three Town cruisers and HMS "Newfoundland" and HMS "Ceylon", had only a single main 274 director, limiting their surface effectiveness) Type 277Q and 293Q for height-finding and surface warning, Type 960M for air warning, and 974 for surface warning. In order to save weight, her torpedo armament was removed. Modern passive sonar type 174, 176 was installed and noise-reducing rubber insulation fitted to the propeller shaft.


title: HMS Belfast

text: "Belfast" arrived in Singapore on 16 December 1959, and spent most of 1960 at sea on exercise, calling at ports in Hong Kong, Borneo, India, Ceylon (now Sri Lanka), Australia, the Philippines and Japan. On 31 January 1961, "Belfast" recommissioned, under the command of Captain Morgan Morgan-Giles. On her final foreign commission "Belfast" joined a number of exercises in the Far East, and in December 1961 she provided the British guard of honour at Tanganyika's independence ceremony in Dar-es-Salaam.