Question

A plot of angle of deviation Dersus of incidence for a triangular prism is shown below.
The angle of incidence for which the light ray travels Angle of inc parallel to the base is

• A. $30^{\circ }$
• B. $60^{\circ }$
• C. $45^{\circ }$
• D. Data insufficient

Answer 1

Answer: (C)

When light ray travels parallel to the base, the light suffers minimum deviations.
So, for minimum deviation, $D_{\min }=40^{\circ }$
$i=e=45^{\circ }$ (from graph)