There is a small source of light at some depth below the surface of water (refractive index =4/3 ) in a tank of large cross sectional surface area.…

There is a small source of light at some depth below the surface of water (refractive index $\displaystyle =\frac{4}{3}$ ) in a tank of large cross sectional surface area. Neglecting any reflection from the bottom and absorption by water, percentage of light that emerges out of surface is (nearly) : [Use the fact that surface area of a spherical cap of height h and radius of curvature r is $\displaystyle 2 \pi \mathrm{rh}]$