JEE Main 2015PhysicsRay OpticsHardMCQ

JEE Main 2015 — Ray Optics Question with Solution

JEE Main 2015 (11 Apr Online)

Question

A thin convex lens of focal length f 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 a3 in front of the combination. The value of a is:

Choose an option

Show full solutionCorrect option: A
Correct answer
A2f

Step-by-step explanation


Equivalent power of combination is

Peff=2Plens+Pmirror ...(i)

∵Pmirror =0 for plane mirror and Plens=1f

Also combination behaves as a mirror. So. Peff=1fmirror

In equation (i)

-1fmirror =2f⇒fmirror=-f2

By mirror formula

1fmirror =1u+1v

Here u= -a, v=-a3, fmirror= -f2

⇒-2f=1-a+3-a=-4a

⇒-2f=-4a⇒a=2f

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About this question

This is a previous-year question from JEE Main 2015, covering the Ray Optics chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.