question_answer

A thin convex lens of focal length T is put on a plane mirror as shown in the figure.

When an object is kept at a distance 'a' from the lens - mirror combination, its image is formed at a distance\[\frac{a}{3}\]in front of the combination. The value of 'a' is:                                                            [JEE MAIN 11-04-2015]

A) f

B) 2f

C) 3f

D) \[\frac{3}{2}f\]

Correct Answer: B

Solution :

[b]

This combinations will behave like a mirror of power.

so the behaviour will be like a mirror of focal length

Using mirror equation