Question

Figure shows the graph of angle of deviation $\delta$ versus angle of incidence $i$ for a light ray striking a prism. The prism angle is

• A. ${30}^{\circ }$
• B. ${45}^{\circ }$
• C. ${60}^{\circ }$
• D. ${75}^{\circ }$

Answer 1

The correct option is B ${45}^{\circ }$

By comparing the graph with the standard plot we get:



$\delta ={30}^{\circ },i_1={15}^{\circ },i_2={60}^{\circ }$

We know that,
$\delta =i_1+i_2-A$

$\Rightarrow$${30}^{\circ }={15}^{\circ }+{60}^{\circ }-A$

$\therefore$ $A={45}^{\circ }$

Hence, option (b) is the correct answer.

Why this question? This question tests the graphical analysis of $\delta$ vs $i$ graph for a prism.