Refraction of Light
Bending of light rays when light travels from one medium into another medium is called refraction of light.
When light enters from less dense medium (faster medium) into the denser medium (slow medium) it bends towards the normal to the boundary which separates the two mediums. When light enters into denser medium to less dense medium it bends away from the normal at point of entry of light rays.
Examples of refraction:
Our eyes function based on refraction to make images inside them. Sparkling of diamonds. Mirages. Beautiful rainbows are the result of refraction.
If we dip a pencil into a clear cup of water, the pencil looks bent or broken due to the refraction of light. When light enters from air to water it slows down and bend towards the normal (horizontal line at point of entry into water) which makes the part of the pencil immersed look bent or broken.
Please note that reflection and refraction of light are two different phenomenons.
Below is a link to a lesson plan explaining phenomenon of refraction in detail
Click on the above link to download a comprehensive lesson to know all about refraction of light