Note: Mcqs related to Physical optics will be updated on this page.Answers to the mcqs will be given in the comments section.

[page][item] 1-One cannot see through fog because
A- Fog absorbs light
B- The refractive index of fog is infinity
C- Light suffers total reflection at the droplet of fog
D- Light is scattered by the droplets in fog

2-At sunrise or sunset, the sun looks reddish because
A The sun is coldest at these times
B Of the effects of reflection and refraction
C The sun is hottest at these times
D Of the scattering of light

3-A prism splits a beam of white light into its seven constituent colors. This is so because
A Phase of different colors is different
B Amplitude of different colors is different
C Energy of different colors is different
D Velocity of different colors is different

4-The twinkling of stars is due to
A The fact that stars do not emit light continuously
B The refractive index of the earth's atmosphere fluctuates
C Intermittent absorption of starlight by its own atmosphere
D None of these


5-Light appears to travel in straight lines since
A It is not absorbed by the atmosphere
B It is reflection by the atmosphere
C Its wavelength is very small
D Its velocity is very large

6-Which of the following phenomena is not explained by Huygen's construction of wavefront?
A Reflection
B Reflraction
C Diffraction
D Origin of spectra

7-If yellow light emitted by sodium lamp in Young's double slit experiment is replaced by monochromatic blue light of the same intensity
A Fringe width will decrease
B Fringe width will increase
C The fringe width will remain unchanged
D Fringes will become less intense

8-In Young's experiment, two coherent sources are placed 0.90 mm apart and the fringes are observed one meter away. If it produces the dark fringe at a distance of 1 mm from the central fringe the wavelength of monochromatic light used would be
A 60 x 10^-4 cm
B 10 x10^-4 cm
C 10 x 10^-5 cm
D 6 x 0^-5 cm

9-The contrast in the fringes in any interference pattern depends on
A Fringe width
B Intensity ratio of sources
C Distance between slits
D Wavelengths


10-Huygen's wave theory of light cannot explain
A Diffraction
B Interference
C Polarization
D Photoelectric effect

[/item][item] 11-The sky appears blue because
A Red light is absorved
B Blue light is scattered the most
C Blue light is absorbed
D It is its natural color

12-Interference was observed in interference chamber when air was present, now the chamber is evacuated and if the same light is used, a careful observer will see
A No interference
B Interference with bright bands
C Interference with dark bands
D Interference in which breadth of the fringe will be slightly increase

13-Fraunhoffer spectrum is a
A Line absorption spectrum
B Band absorption spectrum
C Line emission spectrum
D Band emission spectrum

14-The speed of light in air is 3 x 10^8 m/s. What will be its speed in diamond whose refractive index is 2.4?
A 3 x 10^8 m/s
B 332 m/s
C 1.25 x 10^8 m/s
D 7.2 x 10^8 m/s


15-When light travels from one medium to another, which are separated by a sharp boundary, the characteristic which does not change is
A Velocity
B Wavelength
C Frequency
D Amplitude

16-Ray optics is valid when characteristic dimensions are
A Of the same order as the wavelength of light
B Much smaller than the wavelength of light
C Of the order of one millimeter
D Much larger than the wavelength of light

17-When seen in green light, the saffron and green portions of our National Flag will appear to be
A Black
B Black and green respectively
C Green
D Green and yellow respectively

18-If a source of light is moving away from stationary observer, then frequency of light wave appear to change because of
A Doppler's effect
B Interference
C Diffraction
D None f the above

19-For the sustained interference of light, the necessary condition os that the two sources should
A Have constant phase difference
B Be narrow
C Be close to each other
D Of same amplitude


20-A thin lens of focal length f has aperture d. It forms an image of intensity I. Inner part of the lens up to n diameter d/2 is painted black, the intensity of the image will be
A I/4
B I/2
C 3I/4

[/item][item] 21-In the Young's double slit experiment the separation between the slits is halved and the distance between slits and the screen is doubled. The fringe width is
A Halved
B Unchanged
C Doubled
D Quadrupled

22-When the light is incident on polarizing angle which of the following is completely polarized?
A Reflected light
B Refracted light
C Both reflected and refracted light
D Neither reflected nor refracted light

23-Signal from a remote control to the device operated by it travels with the speed of
A Sound
B Light
C Ultrasonic
D Supersonic

24-In Young's double slit experiment on interference, the ratio of the intensities of a bright and a dark band is 6:1. The ratio of the amplitudes of the interfering waves is
A 16
B 5/3
C 4
D 1/4


25-In a spectrometer experiment, monochromatic light is incident normally on a diffraction grating having 4.5 x 10^5 lines per meter. The second order line is seen at an angle of 30 degrees to the normal. What is the wavelength of the light?
A 200 nm
B 430 nm
C 500 nm
D 556 nm

26-A light of wavelength lambda is incident on a diffraction grating on which the slit spacing is equal to 3 lambdas. What is the sine of the angle between the second order maximum and the normal?
A 1/6
B 1/3
C 2/3
D 1

27-Which of the following frequency ranges includes most of the electromagnetic waves emitted by the ultra-violet tubes used in a sun bed?
A 5 x 10^5 to 5 x 10^8 Hz
B 5 x 10^8 to 5 x 10^11 Hz
C 5 x 10^11 to 5 x 10^14 Hz
D 5 x 10^14 to 5 x 10^17 Hz

29-Ultra-violet rays differ from X-rays in that ultra-violet rays
A Cannot be diffrated
B Cannot be polaarized
C Do not affect a photographic plate
D Have a lower frequency

29-The meter was defined in terms of the wavelength lambda of the orange spectral line emitted by excited atoms of Krypton-86. Thus 1 meter=n.lambda, where n is the number of wavelengths in a meter of vacuum. What is the best value for n
A 1.43 x 10^4
B 1.65 x 10^6
C 2.00 x 10^8
D 3.33 x 10^12


30-Which of the following gives three regions of the electromagnetic spectrum in order of increasing wavelength?
A Gamma rays, microwaves, visible radiation
B Radio waves, ultraviolet, x-rays
C Ultraviolet, infrared, microwaves
D Visible radiation, gamma rays, radio waves


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