JEE Main 2019PhysicsRay OpticsHardMCQ

JEE Main 2019 — Ray Optics Question with Solution

JEE Main 2019 (10 Jan Shift 1)

Question

A plano-convex lens of refractive index μ1 and focal length f1 is kept in contact with another plano-concave lens of refractive index μ2 and focal length f2. If the radius of curvature of their spherical faces is R each and f1=2f2, the μ1 and μ2 are related as:

Choose an option

Show full solutionCorrect option: D
Correct answer
D2μ1-μ2=1

Step-by-step explanation

Given,

f1=2f2

Lens maker formula for the first lens is given by,

1f1=μ1-11R-1∞      ...(1)

Lens maker formula for the second lens is given by,

1f2=μ2-11R-1∞      ...(2)

After 12, we get:

f2f1=μ1-1μ2-1=12

⇒2μ1-2=μ2-1

⇒2μ1-μ2=1

Practice this on the real CBT interface

Solve this JEE Main question (and the rest of the Ray Optics chapter) on PrepSharp's TCS iON-style CBT player — with timer, bookmarks and session analytics.

Solve interactively →

About this question

This is a previous-year question from JEE Main 2019, 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.