First slide

The lens

Question

A plano-convex lens fits exactly into a plano-concave lens. Their plane surface are parallel to each other. If the lenses are made of different material of refractive indices $μ_{1}$ and $μ_{2}$ and R is the radius of curvature of the curved surface of the lenses, then focal length of the combination is

Moderate

A

$\frac{R}{μ_{1} - μ_{2}}$
B

$\frac{2 R}{μ_{2} - μ_{1}}$
C

$\frac{R}{2 (μ_{1} - μ_{2})}$
D

$\frac{R}{2 - (μ_{1} + μ_{2})}$

Solution

$\frac{1}{F} = \frac{1}{f_{1}} + \frac{1}{f_{2}} \Rightarrow \frac{1}{F} = (μ_{1} - 1) (\frac{1}{\infty} + \frac{1}{R}) + (μ_{2} - 1) (\frac{1}{- R} - \frac{1}{\infty}) = \frac{μ_{1} - μ_{2}}{R} \Rightarrow F = \frac{R}{μ_{1} - μ_{2}}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App