(i) The phenomenon of the splitting up of the white light into its constituent colours is called dispersion of light.
Dispersion of light is caused because different constituent colours of light offer different refractive indexes to the material of the prism.
(ii) The formation of the rainbow is caused by the dispersion of the white sunlight into its constituent colours.
(iii) Based on the dispersion of white light into its constituent colours, we can conclude that-
(a) the white light consists of seven colours.
(b) the violet light suffers maximum deviation and the red light suffers minimum deviation.