• # question_answer A microscope is focused on a needle lying is am empty tank. Now, the tank is filled with benzene to a height 120 mm. The microscope is moved 40mm to focus the needle again the refractive index of benzene is: A)  $1.5$                         B)  $2.5$C)  $3.0$                         D)  $4.5$

As $\mu =\frac{\text{Real depth}}{\text{Apparent depth}}=\frac{120}{120-40}=1.5$