Question

A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?

Answer 1

$h_1=12.5cm;h_2=9.4cm$

$\mu =h_1/h_2=1.33$

now water is replaced by ${\mu }^{\prime }=1.63$

${\mu }^{{}^{\prime }}=h/y\Rightarrow y=7.67cm$

distance by which microscope should be moved up is $9.4-7.67=1.73cm$