An air bubble inside a glass slab (µ=1.5) appears 6 cm when viewed from one side and 4 cm when viewed from the opposite side. The thickness of the slab is

Options

A. 10 cm
B. 6.67 cm
C. 15 cm
D. none of these

Answer

C

Explanation

We know that, `mu="real depth"/"apparent depth"`
Let the thickness of the slab bet and real depth of the bubble from one side be x. Then,
`=mu="real depth"/"apparent depth" implies 1.5 =(t-x)/4=x/6`
`:. X=9 and t=15 cm`