Question

A convex spherical mirror, whose focal length has a magnitude of 21.2 cm, is to form an image 12.2 cm behind the mirror.

(a) Where should the object be placed?

(b) What is the magnification of the mirror?

Answer 1

given

focal length f = - 21.2 cm

image distance v = - 12.2 cm

a )

using the equation 1/f = 1/u + 1/v

1/u = 1/f - 1/v

= -1/21.2 + 1/12.2

the object should be placed at a distance is u = 28.737 cm

b )

M = - v / u

= 12.2 / 28.737

the magnification of the mirror is M = 0.4245