Question

Why doest the angle of deviation first decrease on increasing the angle of incidence in a prism ?
Give proper reason.

Answer 1

Answer: Here's your answer

Explanation:

The deviation angle in a prism depends upon: Refractive index of the prism: The refractive index depends on the material and the wavelength of the light. ... The deviation angle first increases with increasing incidence angle, and then decreases.

Answer 2

In Minimum Deviation, the refracted ray in the prism is parallel to its base. In other words, the light ray is symmetrical about the axis of symmetry of the prism.[1][2][3] Also, the angle of incidence and angle of emergence equal each other ( {\displaystyle i=e} {\displaystyle i=e}). And, the angles of refractions are equal i.e. {\displaystyle r_{1}=r_{2}.} {\displaystyle r_{1}=r_{2}.}........