Ray Optics & Optical Instruments  MCQs

MCQs of Ray Optics & Optical Instruments

Showing 61 to 70 out of 143 Questions
4 5 6 7 8 9
61.
A convex lens is dipped in a liquid, whose refractive index is equal to the refractive index of the lens. Then its focal length will _____ .
(a) become zero
(b) remain unchanged
(c) become infinite
(d) None of these
Answer:

Option (c)

62.
Velocity of light in diamond, glass and water decreases in the order of _____ .
(a) Water > glass > diamond
(b) Diamond > glass > water
(c) Diamond > water > glass
(d) Water > diamond > glass
Answer:

Option (a)

63.
If the power of the lens is +5 D, then its focal length is _____ cm.
(a) 20
(b) -20
(c) 60
(d) -60
Answer:

Option (a)

64.
The power of combination of two lenses of powers +1.5 D and -2.5 D is _____ .
(a) 1.5 D
(b) -2.5 D
(c) -1 D
(d) +D
Answer:

Option (c)

65.
A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination is _____ .
(a) -6.5 D
(b) +6.5 D
(c) +1.5 D
(d) -1.5 D
Answer:

Option (d)

66.
If two lenses of power 2 D and 3 D are kept in contact with each other, then focal length of the combination will be _____ cm.
(a) 5
(b) 10
(c) 20
(d) 25
Answer:

Option (c)

67.
Rainbow is formed due to _____ .
(a) refraction and dispersion
(b) refraction and scattering
(c) diffraction and reflection
(d) refraction and reflection
Answer:

Option (a)

68.
A small angled prism of refractive index 1.7 gives a deviation of 4.9°. The angle of prism is _____ .
(a) 5°
(b) 7°
(c) 9°
(d) 11°
Answer:

Option (b)

69.
The refractive index of material of prism for blue and red colours of rays are 1.532 and 1.514 respectively. If angle of prism is 8°, then angular dispersion produced by the prism is _____ .
(a) 0.072°
(b) 0.144°
(c) 0.288°
(d) 0.555°
Answer:

Option (b)

70.
The danger signal of light is red, because red colour is least _____ .
(a) reflected
(b) refracted
(c) dispersed
(d) scattered
Answer:

Option (d)

Showing 61 to 70 out of 143 Questions
4 5 6 7 8 9