Light reflection and refraction Worksheet-5

Light reflection and refraction Worksheet-5

 

  1. When a ray of light travels from water to glass, it bends

A. Towards normal

B. Away from normal

C. Neither towards nor away from normal

D. Cannot say

 

  1. No refraction occurs when ray goes from

A. Rarer to denser medium

B. Denser to rarer medium

C. One medium to other medium of same optical density

D. Cannot say

 

  1. Refractive index of glass w.r.t. air is 3/2. What is the refractive index air w.r.t glass ?

A. 2/3                 B. 1                      C. Zero               D. (3/2)2

 

  1. The apparent depth of a tank of water is 3 m. what characteristic that remains unaffected is

A. 4 m                 B. 3 m                 C. 7 m                 D. 1 m

 

  1. Focal length of a lens depends on

A. Object distance                        B. Image distance

C. Nature of material                  D. None of these

 

  1. Power of a convex lens of focal length 50 cm is

A. –2 D              B. –(1/2)D        C. 2D                  D. (1/2)D

 

  1. A convex lens of focal length 15 cm is used to form an image of the size of the object. Where form the lens should the object be placed ?

A. 15 cm             B. 30 cm            C. 60 cm            D. 10 cm

 

  1. To form an image twice the size of the object,, using a convex lens of focal length 20 cm, the object distance must be

A. < 20 cm

B. > 20 cm

C. < 20 cm and between 20 cm and 40 cm

D. Cannot say

 

  1. Which one of the following materials cannot be used to make a lens?

A. Water            B. Glass              C. Plastic           D. Clay

 

  1. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

A. between the focus and centre of curvature,

B. at the centre of curvature,

C. beyond the centre of curvature,

D. Between the pole of the mirror and focus.

 

  1. Where should an object be placed in front of a convex lens to get a real image of the size of the object ? 

A. At the principal focus of the lens,

B. At twice the focal length,

C. At infinity,

D. Between the optical centre of the lens and its principal focus.

 

  1. A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The mirror and lens are likely to be

A. Both are concave.

B. Both are convex

C. The mirror is concave, but the lens is convex.

D. The mirror is convex, but the lens is concave.

 

  1. No matter how far you stand from a spherical mirror, your image appears erect. The mirror is likely to be

A. plane                                          B. concave

C. convex                                       D. either plane or convex.

 

  1. Which of the following lenses would you prefer to use while reading small letters found in a dictionary ?

A. Convex lens of focal length 50 cm

B. A concave lens of focal length 50 cm

C. A convex lens of focal length 5 cm

D. A concave lens of focal length 5 cm.

 

Answer Key:

  1. A
  2. C
  3. A
  4. A
  5. C
  6. C
  7. B
  8. C
  9. D

Clay cannot be used to make a lens as it is not transparent.

  1. D

For virtual, erect and larger image, the object must lie between the pole of the mirror and its focus.

  1. B

The object is to be placed at twice the focal length of the lens.

  1. A

As per New Cartesian Sign Conventions, the focal length of a concave mirror and focal length of a concave lens, both are negative. Therefore, both are concave.

  1. D

The image is erect in a plane mirror and also in a convex mirror, for all positions of the object.

  1. C

For reading small letters in a dictionary, we should use a convex lens of smaller focal length.