Qs : Ray Optics


Most of these questions are from past AIPMT (Screening) exam:

Q1) Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of lens when immersed in a liquid of refractive index of 1.25 will be     [1988]
(a) 10 cm     (b) 2.5 cm     (c) 5 cm   (d) 7.5 cm

Q2) A ray is incident at an angle of incidence I on one surface of a prism of small angle A and emerge normally from opposite surface. If the refractive index of the material of prism is µ, the angle of incidence I is nearly equal to      [1989]
(a) A/ µ        (b) A/2µ        (c) µA      (d) µA/2

Q3) Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is 1.5  is   [1993]
(a) 2x10-4 s     (b) 2x108 s      (c) 2x10-11 s      (d) 2x1011 s

Q4) A point source of light is placed 4 m below the surface of water of refractive index 5/3. The minimum diameter of a disc, which should be placed over the source, on the surface of water to cut off all light coming out of water is            [1994,2001]
(a) infinite     (b) 6 m       (c) 4 m        (d) 3 m

Q5) Electromagnetic radiation of frequency v frequency, velocity v and wavelength l, in air, enters a glass slab of refractive index µ. The frequency, wavelength and velocity of light in the glass slab will be, respectively      [1997]
(a) v/µ, l/µ, v    (b) v, l, v/µ   (c) v, l/µ, v/µ     (d) v/µ, l/µ, v/µ

Q6) A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm. On the other side of the lens, at what distance from the lens, a convex mirror of radius of curvature 10 cm, be placed in order to have an upright image of the object coincident with it?      [1998]
(a) 12 cm      (b) 30 cm      (c) 50 cm      (d) 60 cm

Q7) Light enters at an angle of incidence in a transparent rod of refractive index µ. For what value of the refractive index of the material of the rod the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence?  [1998]

(a) µ > squareroot of 2     (b) µ = 1       (c) µ = 1.1    (d) µ = 1.3

Q8) Colours of thin soap bubbles are due to      [1999]
(a) refraction  (b) dispersion   (c) interference  (d) diffraction

Q9) A planoconvex lens is made of material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is    [1999]
(a) 50 cm        (b) 100 cm     (c) 200 cm       (d) 400 cm

Q10) A man is 6 feet tall. In order to see his entire image, he requires a plane mirror of minimum length equal to    [2000]
(a) 6 ft     (b) 12 ft     (c) 2 ft   (d) 3 ft

Q11) A planoconvex lens is made of a material of refractive index µ = 1.5. The radius of curvature of curved surface of the lens is 20 cm. If its plane surface is silvered, the focal length of the silvered lens will be   [2000]
(a) 10 cm     (b) 20 cm       (c) 40 cm      (d) 80 cm

Q12) A transparent cube contains a small air bubble. Its apparent distance is 2 cm when seen through one face and 5 cm when seen through other face. If the refractive index of the material of the cube is 1.5, the real length of the edge of cube must be     [2000]
(a) 7 cm      (b) 7.5 cm       (c) 10.5 cm       (d) 14/3 cm

Q13) A body is located on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens. The lens is placed at a distance d ahead of second wall, then the required focal length will be      [2002]
(a) only d/4    (b) only d/2
(c) more than d/4 but less than d/2
(d) less than d/4



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