Question

An object P is focussed by a microscope M. A glass slab of thickness 2.1 cm is introduced between P and M. If the refractive index of the slab is 1.5, by what distance should the microscope be shifted to focus the object again ?

Answer 1

The thickness of the glass is d = 2.1 cm and m = 15

Shift due to the glass slab,

$\text{Dt}=[1-\left(\frac{1}{\mu }\right)]d$

$=[1-\left(\frac{1}{1.5}\right)]\left(2.1\right)$

$=\frac{1}{3}\left(2.1\right)=0.7\text{cm}$

So, the microscope should be shifted 0.70 cm to focus the object again.