An image in a convex lens is upright and magnified 3 times. If the focal length of the lens is 15 cm. What is the object distance?

A. 10 cm
B. 25 cm
C. 16 cm
D. 14 cm

Correct Answer:

Option A = 10 cm

Explanation

m = v/u = -3
v = -3u
f = 15cm
1/v + 1/U = 1/f
1/-3U + 1/u = 1/15
2/3u = 1/15
3U = 15 x 2
U = 30/3
= 10 cm