Question

An object is placed at a distance of 25 cm on the axis of a concave mirror, having focal length 20 cm. Find the lateral magnification of an image.(A) 2
(B) 4
(C) -4
(D) -2

Answer 1

Refer to the attachment.

(C) m = - 4

Hope it helps u ✌ ✌

Answer 2

Lateral magnification, m = - 4

Explanation:

For spherical mirrors,  

1/v + 1/u =1/f

Given f = -20 cm and u = -25 cm, we can solve for v.

1/v = 1/f – 1/u  

= (1/-20) -  (1/-25)

= -1/20 + 1/25

= -(5+4)/100

= -100

We get v = -100 cm.

Lateral magnification, m = - v/u = - (-100) / (-25) = - 4