Question

A plano convex lens is silvered at its surface the refractive index and radius of curvature of the lens are 3/2 and 30cm respectively then the effective focal length will be

Answer 1

Given that,

Refractive index $\mu=\dfrac{3}{2}$

Radius of curvature = 30 cm

We need to calculate the focal length

Using formula of focal length

$\dfrac{1}{F}=\dfrac{2\mu}{R}$

Where, F = focal length

R = radius of curvature

$\mu$ = refractive index

Put the value into the formula

$\dfrac{1}{F}=\dfrac{2\times3}{2\times30}$

$\dfrac{1}{F}=\dfrac{1}{10}$

$F=10\ cm$

Hence, The focal length is 10 cm.