Question

(a) Explain why, a stick half immersed in water appears to be bent at the surface. Draw a labelled diagram to illustrate your answer.
(b) A coin in a glass tumbler appears to rise as the glass tumbler is slowly filled with water. Name the phenomenon responsible for this effect.

Answer 1

(a) When a stick is half immersed in water, it appears to be bent at the surface due to the refraction of light.


In the above figure, the half portion BO of stick AO is immersed in water and it appears to be bent at point B. The light ray OC coming from the lower end O of the stick passes from water to air and gets refracted away from the normal in the direction CX. Another ray OD is refracted in the direction DY. These two refracted rays, i.e, CX and DY meet at point I, when produced backwards. The point I is nearer to the water surface than point O. Therefore, a virtual image of end O of the stick is formed as I.
So, human eye at position E sees the end O at I; i.e., stick appears to be bent.

(b) A coin in a glass tumbler appears to rise as the glass tumbler is slowly filled with water. It occurs because of refraction.