A graph is plotted between the angle of deviation ( δ) and angle of incidence (i) for a prism. The nearly correct graph is
For a prism, as the angle of incidence increases, the angle of deviation first decreases goes to a minimum value and then increases.
It is found that the angle of deviation becomes minimum when the angle of incidenece is equal to angle of emergence
Deviation is minimum,
when i = e
or r1=r2
δmin=i+e−A=2i−A (i = e)