question_answer

    A transparent cube of 0.21 m edge contains a small air bubble. Its apparent distance when viewed through one face of the cube is 0.10 m and when viewed from the opposite face is 0.04 m. The actual distance of the bubble from the second face of the cube is

A)  0.06m                                  

B)  0.17m

C)  0.05m                                  

D)  0.04m

Correct Answer: A

Solution :

                \[Refractive\text{ }index=\frac{real\,depth}{apparent\text{ }depth}\] \[\therefore \] \[\frac{x}{0.04}=\frac{0.21-x}{0.10}\] \[\Rightarrow \]               \[0.21\times 0.04-x\times 0.04=0.10x\] \[\Rightarrow \]               \[x=\frac{0.21\times 0.04}{0.14}=0.06\,m\]