Q. A transparent cube of 2.1 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) 0.06 m
B) 0.17 m
C) 0.05 m
D) 0.04 m
Explanation
(a) $Refractive\ index = \frac{real\ depth}{apparent\ depth}$
$\therefore\frac{x}{0.04} = \frac{0.21 - x}{0.10}$
$\Rightarrow \ 0.21 \times 0.04 - x \times 0.04 = 0.10x$
$\Rightarrow \ x = \frac{0.21 \times 0.04}{0.14} = 0.06\ m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.