Equation gives the relation between the angle of deviation d of a light ray incident on a spherical drop of water in terms of

Equation gives the relation between the angle of deviation ф_d of a light ray incident on a spherical drop of water in terms of the incident angle θ₁ and the index of refraction of water.

(a) Assume that n_air = 1, and differentiate ф_d with respect to θ₁.

(b) Set dф_d/dθ₁ = 0 and show that the angle of incidence θ_1m for minimum deviation is given by

And find θ_1m for water, where the index of refraction for water is 1.33.

n - 1 cos Om 3