An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre ‘O' of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O', principal focus F and height of the image on the diagram.

A convex lens is immersed in a liquid of refractive index greater than that of glass. How will the nature of lens change?

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is directed parallel to the principal axis of a convex mirror. Mark on it the angle of incident and the angle of reflection.

Draw a labelled ray diagram to show the formation of image of an object by a convex mirror. Mark clearly the pole, focus and centre of curvature on the diagram.

List two properties of the images formed by convex mirrors. Draw ray diagram in support of your answer.

Light travels more quickly through water than through glass:

1. Which is optically denser: Water or glass?
2. If a ray of light passes from glass into water, which way will it bend: Towards the normal or away from the normal?

What are the important differences between looking at a photograph of your face and looking at yourself in a plane mirror?

Refractive indices of four media A, B, C and D are given below:

Medium	Refractive index
A B C D	1.33 1.44 1.52 1.65

In which of these four media is the speed of light:

1. Maximum, and
2. Minimum?

Why does a driver prefer to use a convex mirror as a rear-view mirror in a vehicle?

State and define the S.I. unit of power of a lens.