A pencil standing in a glass of water appears bent at the water's surface. This happens because of

हल

1. 01

   Light travels at different speeds in air and in water, so it changes direction as it crosses the boundary between them. That bending is refraction.

2. 02

   The light from the submerged part of the pencil reaches the eye along a bent path, and the eye reads it as coming from a shifted position.

3. 03

   Reflection would bounce the light back, dispersion splits white light into colours, and diffraction is the spreading of light around an obstacle.