How to make a rainbow?

 

To make a rainbow we need :a light, a prism and if you want a black cover.For better result go in a dark room. 

To make a rainbow you need to place the black cover in front of the light and place the prism in front of the light. To see the rainbow better you can place a white paper in front of the light. 

To make more than one rainbow you can use a black cover with two or three slit.

This phenomenon appends when the light touch a substance with a different refrative index.