Ray Optics & Optical Instruments  MCQs

MCQs of Ray Optics & Optical Instruments

Showing 21 to 30 out of 143 Questions
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.
(a) bu-ff2
(b) bfu-f
(c) u-ff
(d) bfu-f2
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 ?
(a) 2n·h
(b) 2hn
(c) 2hn-1
(d) h1+1n
Answer:

Option (b)

23.
A concave mirror had radius of curvature of 0.2 m. Its focal length is _____ .
(a) -0.1 m
(b) 0.1 m
(c) -0.2 m
(d) 0.4 m
Answer:

Option (a)

24.
To a bird in air, a fish in water appears to be at 30 cm from the surface. If μw= 43, then the true depth of the fish is _____ .
(a) 30 cm
(b) 45 cm
(c) 40 cm
(d) None of the above
Answer:

Option (c)

25.
According to Rayleigh scattering, intensity of scattered light is _____ of the intensity of incident light.
(a) proportional to fourth power
(b) inversely proportional to square
(c) proportional to square
(d) inversely proportional to fourth power
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 _____ .
(a)
(b) λn
(c) λn2
(d) n2λ
Answer:

Option (b)

27.
A critical angle for a medium is 60°. The refractive index of the medium will be _____ .
(a) 32
(b) 23
(c) 13
(d) 3
Answer:

Option (b)

28.
The focal length of a convex lens μg = 32 in air is 20 cm. When immersed in water μw = 43 , its focal length will be _____ .
(a) 80 cm
(b) 26.7 cm
(c) 20 cm
(d) 5 cm
Answer:

Option (a)

29.
The colour of light is due to which property of light ?
(a) Wavelength
(b) Velocity
(c) Amplitude
(d) Frequency
Answer:

Option (d)

30.
A cylindrical lens is required to correct _____ .
(a) Myopia
(b) Astigmatism
(c) Hypermetropia
(d) Presbyopia
Answer:

Option (b)

Showing 21 to 30 out of 143 Questions