Class 12 Ray Optics And Optical Instruments CBSE Questions & Answers

Class 12 · Ray Optics And Optical Instruments

This is Physics Class 12 Ray Optics and Optical Instruments CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
Magnification produced by a lens m is given by
  • A
    \({u \over v}\)
  • B
    \({v \over u}\)
    Correct
  • C
    -\({v \over u}\)
  • D
    - \({u \over v}\)
2
The power P of a lens is given by the approximate formula
  • A
    \({2 \over {f}}\)
  • B
    \({3 \over {f}}\)
  • C
    \({1 \over {f}}\)
    Correct
  • D
    \({1 \over {2f}}\)
3
Domestic power supply in India is
  • A
    230 V 50 Hz
    Correct
  • B
    416 V 60 Hz
  • C
    110 V 60 Hz
  • D
    24 V DC
4
If several thin lenses of focal length \({{\rm{f}}_{\rm{1}}},{\rm{ }}{{\rm{f}}_{\rm{2}}},{\rm{ }}{{\rm{f}}_{\rm{3}}}\), … are in contact, the effective focal length is
  • A
    \({1 \over f} = {1 \over {{f_1}}} - {1 \over {{f_2}}} + {1 \over {{f_3}}} + \ldots \)
  • B
    \({1 \over f} = {1 \over {{f_1}}} + {1 \over {{f_2}}} + {1 \over {{f_3}}} + \ldots \)
    Correct
  • C
    \({1 \over f} = {1 \over {{f_1}}} + {1 \over {{f_2}}} - {1 \over {{f_3}}} + \ldots \)
  • D
    \({1 \over f} = {1 \over {{f_1}}} - {1 \over {{f_2}}} - {1 \over {{f_3}}} + \ldots \)
5
At the minimum deviation \({{\rm{D}}_{\rm{m}}}\), the refracted ray inside the prism
  • A
    becomes at acute angle to its base
  • B
    becomes perpendicular to its base
  • C
    becomes parallel to its base.
    Correct
  • D
    becomes parallel to its sides
6
Dispersion is
  • A
    The phenomenon of splitting of light into its component colours
    Correct
  • B
    The phenomenon of splitting of light into electric and magnetic fields
  • C
    The variation of refractive index from glass to glass
  • D
    The phenomenon of scattering of light from various molecules
7
The bluish color predominates in a clear sky,
  • A
    Since blue has a shorter wavelength than red and is scattered much more strongly
    Correct
  • B
    Since blue has a shorter wavelength than red and is scattered much less strongly
  • C
    Since blue has a is radiated much more strongly
  • D
    Since blue has a longer wavelength than red and is scattered much more strongly
8
Accommodation of the human eye is
  • A
    Ability to change the focal length
    Correct
  • B
    Ability to see an erect image
  • C
    Ability to change the intensity of incoming light
  • D
    Ability to see close by objects
9
Farsighted or hypermetropic eye can be corrected by
  • A
    cylindrical lens
  • B
    converging (positive) lens
    Correct
  • C
    Plano-concave lens
  • D
    diverging lens
10
A plano-convex lens is made of glass of refractive index 1.5. The focal length f of the lens & the radius of curvature R of its curved surface, are related by
  • A
    f = R
  • B
    f = 2R
    Correct
  • C
    f = 3R/2
  • D
    f = R/2
11
A Plano convex lens of curvature of 30 cm & R.I. 1.5, produces a real image of an object kept 90cm from it. The magnification is
  • A
    1.5
  • B
    2.0
    Correct
  • C
    4.0
  • D
    0.5
12
An equi-convex thin lens (\(\mu \) =1.5) of focal length in air as 30cm is sealed into an opening in one end of tank filled with water ((\(\mu \) =1.33). At the end of the tank opposite the lens is a plane mirror, 80 cm distant from the lens. The position of the image formed by the lens-water-mirror system of a small object outside the tank on the lens axis and 90cm to the left of the lens will be
  • A
    41.5 cm to the left of the lens
  • B
    41cm to the right of the lens
  • C
    41.5 cm to the right of the lens
    Correct
  • D
    41 cm to the left of the lens
13
When an astronomical telescope is focused on a distant star, the distance of the eye piece from the objective is 60 cm. When focused on a distant flag post the eye piece must be drawn at 0.1cm. If the focal length of the eye piece is 5cm; what will be the distance of the pole from the objective? Assume that the eye is focused for infinity?
  • A
    302 m
  • B
    30 m
  • C
    300 m
  • D
    303 m
    Correct
14
When a lens is inserted between an object & the screen which are at fixed distance apart, the size of the image is either 6cm or 2/3 cm. The size of the object is
  • A
    4 cm
  • B
    4.33 cm
  • C
    2 cm
    Correct
  • D
    3 cm
15
A far-sighted man who has lost his spectacles reads a book by looking through a small hole in the sheet of paper. Then
  • A
    in doing so, the focal length of the eye lens is effectively decreased
    Correct
  • B
    in doing so, the equivalent focal length remains the same as with
  • C
    in doing so, the focal length of the eye lens is effectively increased
  • D
    the hole produces an image of the letters at a longer distance