The total angle of deviation (δ) of the ray light when it passes through a prism, depends on, (i)the angle of incidence (ii)the angle of the prism, and (iii)the refractive index of the material of prism But refractive index depends on the colour light. Consequently, the total angle of (δ) will also depend on colour of light. It is that red coloured light is least deviated but violetcolouredlight the deviation is maximum.