Question

An air bubble in a glass slab with refractive index $1.5$ (near normal incidence) is $5\,cm$ deep when viewed from one surface and $3\,cm$ deep when viewed from the opposite face. The thickness (in cm) of the slab is

• A. 8
• B. 10
• C. 12
• D. 16

Answer 1

Answer: (C)

12

Answer 2

$d_{ap} = \frac{d_{ac}}{\mu}$
$\left( 5+ 3 \right) = \frac{d_{ac}}{1.5}$
$d_{ac} = \left(5+3\right) \left(1.5\right) = 12 cm$