Question

A graph is plotted between the angle of deviation ( $\delta$) and angle of incidence ($i$) for a prism. The nearly correct graph is

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

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 $r_1=r_2$
${\delta }_{min}=i+e-A=2i-A$ (i = e)