Calculate the refractive index of the material of an equilateral prism for which the angle of minimum deviation is $\frac{\mathrm{\pi }}{3} \mathrm{radian}$.

White light is passed through a prism of angle 10º. If the refractive index for red and violet colours are 1.641 and 1.659 respectively, then find the -

(a) angles of deviation for violet and red colours.

(b) angular dispersion

(c) dispersive power