21. |
A small linear object of length b is placed on the axis of a concave mirror. The end of the object facing the mirror is at a distance u from the mirror. If f is the focal length of a mirror, the length of the object will be _____ approximately.
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Answer:
Option (d) |
22. |
A liquid of refractive index n is filled in a tank. A plane mirror is kept at the bottom of the tank. A point like object (P) is kept at a height h from the mirror on the liquid surface. An observer observes the object and its image in the vertically downward direction from top. How much distance will observe note between P and its image ?
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Answer:
Option (b) |
23. |
A concave mirror had radius of curvature of 0.2 m. Its focal length is _____ .
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Answer:
Option (a) |
24. |
To a bird in air, a fish in water appears to be at 30 cm from the surface. If , then the true depth of the fish is _____ .
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Answer:
Option (c) |
25. |
According to Rayleigh scattering, intensity of scattered light is _____ of the intensity of incident light.
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Answer:
Option (d) |
26. |
If the wavelength of light in vacuum be λ, the wave length in a medium of refractive index n will be _____ .
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Answer:
Option (b) |
27. |
A critical angle for a medium is 60°. The refractive index of the medium will be _____ .
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Answer:
Option (b) |
28. |
The focal length of a convex lens in air is 20 cm. When immersed in water , its focal length will be _____ .
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Answer:
Option (a) |
29. |
The colour of light is due to which property of light ?
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Answer:
Option (d) |
30. |
A cylindrical lens is required to correct _____ .
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Answer:
Option (b) |