range of frequencies of electromagnetic waves that stimulates the retina of the eye

ray model

straight-line path of light


a body that emits light waves


body that reflects light waves from an outside source

luminous flux

rate at which visible light is emitted from a source


unit of luminous flux


illumination of a surface


lumens per square meter


candle power

luminous intensity

the luminous flux that falls on 1m2 of a sphere 1m in radius


transmit light without distortion


transmits light but does not permit objects to be seen clearly


transmits no light, but absorbs or reflects all light


ordered arrangement of colors from violet to red

primary colors

red light, blue light, green light,

secondary colors

yellow, cyan, magenta

complementary colors

any color made up of two primary colors


a molecule that absorbs certain colors and transmits other


a colored material that absorbs certain colors and reflects others

primary pigment

a pigment that only absorbs one color from white light

secondary pigment

a pigment that absorbs two primary colors and transmits one.

thin-flim interference

constructive and destructive interference of light waves


a light that is produced by a polarizing material

regular reflection

light is reflected back in parallel beams.

diffuse reflection

light that is reflected but not image not easily seen.

angle of refraction

angle that the refracted ray makes with the normal to the surface

optically dense

angle of refraction smaller than the angel of incidence

Snell's law

ratio of the sine of the angle of incedence to the sine of the angle of refraction is a constant

index of refraction

light going from vacuum to another medium, the constant n,

total internal refraction

when light reflects completely off the inside wall of a denser medium rather than passing through the wall into a less dense medium

critical angle

the smallest angle of incidence for which light is totally reflected


the separation of light into its spectrum

plane mirror

a mirror with a flat surface, light is reflected by regular reflection


a source of spreading light rays


the image further than what it really is.

virtual image

rays that dont converge at a point

erect image

a mirror image that points in the same direction as the reflected object

concave mirror

reflects light from its inner surface

principal axis

a straight line perpendicular to the surface of a mirror that divides the mirror in half

focal point

parallel rays meet at F

focal length

the distance from the focal point to the mirror along the principal axis

real image

rays that actually converge and pass through the image

virtual image

cannot be projected onto a screen or captured on a piece of paper

lens/mirror equation



the ratio of the size of the image, hi, to the size of the object, ho

spherical aberration

the image formed by parallel rays in a large spherical mirror

convex mirror

spherical mirror that reflects light from its outer surface


made up of transparent material with a refractive index larger than than of air

convex lens

thicker at the center than the edges

concave lens

thinner in the middle than at the edges

chromatic aberration

object viewed through a lens appears ringed with color.

achromatic lens

lens that converges the light

interference fringes

a pattern of bright and dark bands

monochromatic light

emits only one wavelength

coherent waves

when wave crests and troughs reach same point at the same time.

diffraction grating

a device that transmits light and forms an interference pattern in the same way that a double slit does

rayleigh criterion

central bright band of one star falls on the first dark band of the second.

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom


Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

Voice Recording