A small bulb (assumed to be a point source) is placed at the bottom of a tank containing water to a depth of `80 cm`. Find out the area of the surface of water through which light from thr bulb can emerge. Take the value of refractive index of water to be `4//3`.

Explanation

`r=0.8xxtani_(c) and sin i_(c)=1//1.33~=0.75`, where r is the radius (in m) of the largest circle from which light comes out and `i_(c)` is the critical angle for water-air interface, Area` = 2.6m^(2)`