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
Light rays from a point object
  • A
    radiate only to the side
  • B
    radiate in some lines
  • C
    radiate only at the front
  • D
    radiate in all directions
    Correct
2
According to Cartesian sign convention.
  • A
    all distances are measured from the bottom of the mirror or the lens
  • B
    all distances are measured from the top of the mirror or the lens
  • C
    all distances are measured from infinity
  • D
    all distances are measured from the pole of the mirror or the optical centre of the lens
    Correct
3
According to Cartesian sign convention the heights measured
  • A
    downwards with respect to x-axis and normal to the principal axis (x-axis) of the mirror/lens are taken as positive
  • B
    rightwards with respect to x-axis and normal to the principal axis (x-axis) of the mirror/lens are taken as positive
  • C
    leftwards with respect to x-axis and normal to the principal axis (x-axis) of the mirror/lens are taken as positive
  • D
    upwards with respect to x-axis and normal to the principal axis (x-axis) of the mirror/lens are taken as positive
    Correct
4
Focal length of a mirror is given by
  • A
    f = R/4, R=radius of curvature
  • B
    f = R, R=radius of curvature
  • C
    f = \({{\rm{R}}^{\rm{2}}}\), R=radius of curvature
  • D
    f = R/2, R=radius of curvature
    Correct
5
According to the mirror equation
  • A
    \({1 \over f} = {1 \over u} + {1 \over v}\)
    Correct
  • B
    \({2 \over f} = {1 \over u} + {1 \over v}\)
  • C
    \({1 \over f} = {2 \over u} + {1 \over v}\)
  • D
    \({1 \over f} = {1 \over u} + {2 \over v}\)
6
Magnification for spherical mirrors m is given by
  • A
    \({u \over v}\)
  • B
    \({u \over v}\)
  • C
    - \({v \over u}\)
    Correct
  • D
    \({v \over u}\)
7
Refraction is
  • A
    Reversal of direction of propagation of light
  • B
    None of the above
  • C
    The change of direction of propagation of light
  • D
    Change of direction of propagation of light at the interface of two media as light passes from one medium to another
    Correct
8
According to Snell’s law
  • A
    The ratio of the angle of incidence to the angle of refraction is constant
  • B
    The ratio of the cosine of the angle of incidence to the cosine of angle of refraction is constant
  • C
    The ratio of the sine of the angle of incidence to the sine of angle of refraction is constant
    Correct
  • D
    The ratio of the tangent of the angle of incidence to the tangent of angle of refraction is constant
9
For a rectangular slab, refraction takes place at
  • A
    Three interfaces
  • B
    One interfaces
  • C
    Four interfaces
  • D
    Two interfaces
    Correct
10
Total internal reflection can take place only if light is travelling from
  • A
    No two media
  • B
    any two media
  • C
    Denser to rarer medium
    Correct
  • D
    Rarer to denser medium
11
Total internal reflection can take place only if
  • A
    tan(incidence angle) = 1/\({{\rm{n}}_{{\rm{21}}}}\), \({{\rm{n}}_{{\rm{21}}}}\) = refractive index travelling from 2 to 1
  • B
    incidence angle = 1/\({{\rm{n}}_{{\rm{21}}}}\), \({{\rm{n}}_{{\rm{21}}}}\) = refractive index travelling from 2 to 1
  • C
    cos(incidence angle) = 1/\({{\rm{n}}_{{\rm{21}}}}\)1, \({{\rm{n}}_{{\rm{21}}}}\) = refractive index travelling from 2 to 1
  • D
    sin(incidence angle) = 1/ \({{\rm{n}}_{{\rm{21}}}}\), \({{\rm{n}}_{{\rm{21}}}}\) = refractive index travelling from 2 to 1
    Correct
12
Optical fibre communication uses the principle of
  • A
    light scattering
  • B
    light path reversibility
  • C
    Total internal reflection
    Correct
  • D
    least action
13
For small angles Snell’s law becomes
  • A
    \({{\rm{n}}_{\rm{1}}}{\rm{i}}\) = \({{\rm{n}}_{\rm{2}}}\)
  • B
    \({{\rm{n}}_{\rm{1}}}\)= \({{\rm{n}}_{\rm{2}}}\)r
  • C
    i = r
  • D
    \({{\rm{n}}_{\rm{1}}}{\rm{i}}\) = \({{\rm{n}}_{\rm{2}}}\)r
    Correct
14
Lens maker’s formula is
  • A
    \({1 \over f} = \left( {{n_{21}} - 1} \right)({1 \over {{R_1}}} + {1 \over {{R_2}}})\)
  • B
    \({1 \over f} = \left( {{n_{21}} + 1} \right)({1 \over {{R_1}}} + {1 \over {{R_2}}})\)
  • C
    \({1 \over f} = \left( {{n_{21}} + 1} \right)({1 \over {{R_1}}} - {1 \over {{R_2}}})\)
  • D
    \({1 \over f} = \left( {{n_{21}} - 1} \right)({1 \over {{R_1}}} - {1 \over {{R_2}}})\)
    Correct
15
Thin lens approximation for a lens is
  • A
    \({1 \over v} - {1 \over u} = {1 \over f}\)
    Correct
  • B
    \({1 \over v} + {1 \over u} = {1 \over f}\)
  • C
    \({1 \over v} + {1 \over u} = - {1 \over f}\)
  • D
    \({1 \over v} - {1 \over u} = - {1 \over f}\)