Define the Dispersion of light .

Explanation

Activity to procedure a rainbow in classroom :
1) Take a prism and place it on the table near a vertical white wall.
2) Take a thin wooden plank, make a small hole in it and fix it vertically on the table.
3) Place the prism between the wooden plank and wall.
4) Place a white light source behind the hole of the wooden plank . Switch on the light.
5) Adjust the height of the prism such that the light falls on one of the lateral surfaces.
6) Observe the changes in the emerged ray of the prism.
7) Adjust the prism by slightly rotating it till you get an image on the wall.
8) We observe a band of different colours on the wall.
9) These colours are nearly equal to the colours of the rainbow , i.e. VIBGYOR.