A pencil dipped in water obliquely appears bent at the surface of water.
OR
When a pencil is partly immersed in water and held in a slanting position, it appears to be bent at the boundary separating water and air.

Explanation

1. When a pencil is partly immersed in water and held in a slanting position , the rays of light coming from the immersed part of the pencil emerge from water ( a denser medium ) and enter air ( a rarer medium ) . During this propagation, they bend away from the normal on refration.

2. As a result, the immersed part of the pencil does not appear straight to be raised to the part outside the water, but appears to be raised. Hence, a pencil dipped obliquely in water appears bent at the surface of the water.