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

Given,
Thickness of the glass slab, d = 2.1 cm
Refractive index, μ = 1.5
Shift due to the glass slab is given by,
\[∆ t = \left[ 1 - \left( \frac{1}{\mu} \right) \right]d\]
\[= \left[ 1 - \left( \frac{1}{1 . 5} \right) \right]\left( 2 . 1 \right)\]
\[= \frac{1}{3}\left( 2 . 1 \right) = 0 . 7  cm\]
Hence, the microscope should be shifted by 0.70 cm to focus the object 'P' again.