Question

A lens produces an image of an object on a screen. If a slab of refractive index n is placed in between lens and screen, the screen has to be moved by distance d behind. The thickness of slab is

• A. $nd$
• B. $\frac{n-1}{nd}$
• C. $\frac{(n-1)d}{n}$
• D. $\frac{nd}{n-1}$

Answer 1

The correct option is D $\frac{nd}{n-1}$

Shift in the position of image after introducing slab, $\left(d\right)=t(1-\frac{1}{n})$

$nd=t(n-1)\Rightarrow t=\frac{nd}{(n-1)}$