A point source is placed at a depth `h` below the surface of water (refractive index `= mu`). The medium above the surface of water is air from water.

Answer

`(pi h^(2))/(mu^(2) - 1)`

Explanation

Light comes in air form water where refraction takes place.
`sin i_(C) = (R)/(sqrt(R^(2) + h^(2))) = (1)/(mu), mu^(2) R^(2) = R^(2) + h^(2), R^(2) = (h^(2))/(mu^(2) - 1)`
Area `= pi R^(2) = (pi h^(2))/(mu^(2) - 1)`