A rectangular glass slab rests at the bottom of a trough of water. A ray of light incident on water surface at an angle of `50^(@)` passes through water into glass. What is angle of refraction in glass ? Take `mu` for water `4//3` and `mu` for glass `3//2`.

Explanation

Here, `.^(a)mu_(w) = 4//3` and `.^(a)mu_(g) = 3//2`
`:. .^(a)mu_(w) (.^(a) mu_(g))/(.^(a)mu _(w)) = (3//2)/(4//3) = (9)/(8)`
First refraction is in going from air to water
`.^(a)mu_(g) = (sin i)/(sin r) = (4)/(3) = (sin 50^(@))/(sinr)`
`:. sin r = (3)/(4) sin 50^(@) = (3)/(4) xx 0.766 = 0.5745`
Second refraction is in going from water to glass
`.^(w)mu_(g) = (sin r)/(sin r') = (9)/(8)`
`sin r' = (8)/(9) sin r = (8)/(9) xx 0.5745 = 0.5107`
`:. r' = sin^(-1)(0.5107) = 30.7^(@)`.