Question

An air bubble in a glass slab of refractive index 1.5 is 5 cm deep viewed from one face and 2 cm deep when viewed from the opposite face. The thickness of the slab is

Answer 1

here

thickness of the slab = real depth from one face (d) + real depth from the opposite face (d')

now, we know that

refractive index = real depth / apparent depth

thus, for the one face

1.5 = d / 5 cm

or

d = 7.5 cm

and for the opposite face

1.5 = d'/2cm

or

d' = 3 cm

so, total thickness of the slab will be

T = d + d' = 7.5cm + 3cm

or

T = 10.5 cm