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

Options

A. 2
B. 2.5
C. 1.6
D. 1.5

Answer

D

Explanation

When viewed from face (1)
`n = (x)/(6)`
and when viewed from face (2)
`n = (15- x)/(4)`
` (x)/(6) = (15)/(4) - (x)/(4) rArr (2x + 3x)/(12) = (15)/(4)`
`rArr x = 9 rArr n = (9)/(6) = 1.5. `