Above plot show variation of angle of deviation with angle of incidence for prism angle 60 degree and refractive index 1.5.
formula
Variation in angle of deviation due to change in angle of incidence for a triangular prism
The angle of deviation dependent on the angle of incidence as: δ=i+e−A where δ = angle of deviation i = angle of incidence e = angle of emergence A = angle of the prism A plot between the angle of deviation and angle of incidence is shown in the figure. In general, any given value of δ, except for i=e, corresponds to two values of i and hence of e.