Physics

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

• (a) Water
  

• (b) Glass
  

• (c) Plastic

• (d) Clay

A virtual image, larger than the object can be produced by

• (a) Plane mirror

• (b) Concave lens

• (c) Convex mirror

• (d) Concave mirror

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 principal focus and the centre of curvature
  

• 
  (b) At the centre of curvature
  

• 
  (c) Beyond the centre of curvature
  

• 
  (d) Between the pole of the mirror and its principal focus.

Choose the wrong statement:

• (a) A concave mirror can form a magnified real image

• (b) A concave mirror can form a magnified virtual image

• (c) A convex mirror can form a diminished virtual image

• (d) A convex mirror can form a diminished real image

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.

A convex mirror is used to form an image of a real object. Then the incorrect statement is

• (a) The image is erect

• (b) The image is real

• (c) The image lies between the pole and the focus

• (d) The image is diminished in size

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

• (a) Both concave.
  

• (b) Both convex.
  

• 
  (c) the mirror is concave and the lens is convex.
  

• (d) the mirror is convex, but the lens is concave.

For a real object, a convex mirror always forms an image which is

• (a) Virtual and erect

• (b) Real and magnified

• (c) Real and inverted

• (d) Virtual and inverted

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

• (a) plane
  

• (b) concave
  

• 
  (c) convex
  

• (d) either plane or convex.

At what distance from a concave mirror of focal length 10 cm must an object be placed in order that an image double its size may be obtained?

• (a) Either 5 cm or 15 cm

• (b) At 10 cm

• (c) 5 cm

• (d) 15 cm only