Question

An object is placed at a distance of 15 cm from a convex lens of a focal length 10 cm. On the other side of the lens, a convex mirror is placed at its focus such that the image formed by the combination coincides with the object itself. The focal length of the convex mirror is

(A) 20 cm 

(B) 10 cm 

(C) 15 cm 

(D) 30 cm

Answer 1

The correct option is (B) 10 cm.

Explanation:

Image formed by lens be at distance v₁ from lens

v₂ = +20 cm, because rays retrace their path after reflection.