question_answer 5)

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

Answer:

Using  or or Also, as shown in the figure, if S is thesource and P is the point from where totalinternal reflection starts to occur, then intriangle OSP, or 48°45' = 80 x 1.1403 = 91-22 cm Therefore, area of surface of water = Areaof the circle of radius OP