question_answer

A transparent cube of 15 cm edge contains a small air bubble. Its apparent depth when viewed through one face is 6 cm and when viewed through the opposite face is 4 cm. Then the refractive index of the material of the cube is

A)  2.0                              

B)  2.5

C)  1.6                              

D)  1.5

Correct Answer: D

Solution :

 When viewed from face (1) \[\mu =\frac{u}{v}=\frac{x}{v}=\frac{x}{6}\]                                       (i) Now when viewed from face (2) \[\mu =\frac{15-x}{v}=\frac{15-x}{4}\]                          (ii) From equation (i) and (ii) \[\mu =\frac{15-6\mu }{4}\Rightarrow \mu =1.5\]