Why does a pencil appear to be bent at the surface of separation when placed in water? Explain.

1. It is due to the refraction of light.
2. Consider a pencil AO, such that BO portion of the pencil is immersed in water as shown in figure.
3. Rays of light from the tip (O) of the pencil bend away from the normal as they go from water to air. The refracted rays appear to come from point I.
4. Thus, the immersed portion of pencil in water appears as BI.
5. Hence, the pencil appears to bent at the water surface.
6. Moreover, the immersed portion of the pencil in water also appears to be shorter than the actual length of the pencil.

Hence, a pencil half immersed in water at an angle appears bent due to refraction of light at the air-water surface.