# An air bubble in a glass slab with a refractive index of 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

Given, l = length of the slab x = position of air bubble from one side the total apparent length of slab = 5 + 3 $$\frac{x}{\mu }+(\frac{l-x}{\mu })=8$$ $$(\frac{l}{\mu })=8$$ $$l=8\mu =8*15=12 cms$$