(a) Define optical center of a spherical lens.

(b) A divergent lens has a focal length of20 cm. At what distance should an. object of height 4 cm from the optical centre of the lens be placed so that its image is formed 10 cm away from the lens. Find the size of the image also.

(c) Draw a ray diagram to show the formation of image in above situation.

(a) Optical center of the lens is defined as the point which lies on the principal axis through the rays of light passes without any deflection.

(b) Given: focal length of convex lens = 20 cm

Height of object = 4cm

Applying the lens formula:

Therefore u=-20 cm

Height of image can be calculated by using the formula:

Therefore,

(b)The ray diagram is as follows: