A small bulb is placed at the bottom of a tank containing water to a depth of 80cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33. (Consider the bulb to be a point source.)

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)`