991. Which one of the following cannot be polarized?
A. Radio waves
B. Ultraviolet rays
C. X-rays
D. Sound waves

992. Diffraction fringes are
A. Equally spaced
B. The distance between them increases
C. The distance between then decreases
D. They are adjacent with no space in between

993. In monochromatic red light, a blue book will probably appear to be
A. Black
B. Purple
C. Green
D. No scientific reasoning available

994. A thing that emits its own light is
A. Luminous
B. Non-luminous
C. Incandescent
D. Bright

995. In a double slit experiment if one of the two slit is covered then
A. No interference fringes are observed
B. No diffraction fringes are observed
C. No fringes observed
D. Interference pattern not disturbed

996. Gives the definition of a metre in terms of the wavelength of red cadmium light
A. Newton
B. Einstein
C. Michelson
D. Galileo
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997. In Michelson interferometer to switch the fringe from bright to dark the mirror should be displaced through
A. λ / 2
B. λ/3
C. λ/6
D. λ/4

998. In the shadow of a ball the central portion appears bright that happens due to
A. Interference
B. Diffraction
C. Polarization
D. Refraction
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999. Which experiment shows that the wavelength of light is smaller than that of sound
A. Diffraction
B. Polarization
C. Interference
D. Reflection
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1000. Crystals of a material can behave as
A. Convex lens
B. Interferometer
C. Diffraction grating
D. Concave