• Tags: prism, deviation, dispersion
• Difficulty: Moderate

A prism of angle A causes deviation δ = i_{1} + i_{2} - A (by geometry of the prism).

At minimum deviation: i_{1} = i_{2} = i, r_{1} = r_{2} = A/2, and the ray passes symmetrically through the prism. The refractive index: n = sin((A + δ_m)/2) / sin(A/2).

For a thin prism (small A): δ = (n-1)A, independent of angle of incidence. This is widely used in JEE problems.

Angular dispersion = δ_V - δ_R = (n_V - n_R)A. Dispersive power ω = (n_V - n_R)/(n_Y - 1).