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Ray Optics and Optical Instruments · Question 74

AIPMT 2001MCQMedium📈 Topic in 25% papers+4−1
1

A disc is placed on a surface of pond which has refractive index 5/3. A source of light is placed 4 m below the surface of liquid. The minimum radius of disc needed so that light is not coming out is

  1. 3 m
  2. 6 m
  3. 4 m

Answer

(2) 3 m

Solution

Light escapes only within a cone of semi-vertical angle C (the critical angle); the disc must cover the circle where this cone meets the surface.

[figure]

C = 1 = 35

C = 34

r = h C

= 4 34

= 3 m

Answer: (2)

AIPMT 2001

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2

A bubble in glass slab ( = 1.5) when viewed from one side appears at 5 cm and 2 cm from other side, then thickness of slab is

  1. 3.75 cm
  2. 3 cm
  3. 10.5 cm
  4. 2.5 cm.
AIPMT 2000
3

A tall man of height 6 feet, wants to see his full image. Then required minimum length of the mirror will be

  1. 12 feet
  2. 3 feet
  3. 6 feet
  4. any length
AIPMT 2000
4

A plano-convex lens ( = 1.5) has radius of curvature 10 cm. It is silvered on its plane surface. Find focal length after silvering

  1. 10 cm
  2. 20 cm
  3. 15 cm
  4. 25 cm
AIPMT 2000
5

Rainbow is formed due to

  1. scattering and refraction
  2. internal reflection and dispersion
  3. reflection only
  4. diffraction and dispersion.
AIPMT 2000

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