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

C

Explanation

The thicknes of the glas is d=2.1 cm and m=15
Shift due to the glass slab
`Dt=[1-(/1/mu)]d`
`=[1-(1/1.5)](2.1)`
`=1/3(2.1)=0.7cm`
So, the microscope should be shifted 0.70 cm to focus the object again.