Prism, Dispersion & Scattering question from JEE Main 2026 (21 Jan, Shift 2)

Answer: (c)

1. The first face makes $45^\circ$ with the base, so the horizontal ray meets it at $i = 45^\circ$.
2. $\sin r_1 = \frac{\sin 45^\circ}{\sqrt{2}} = \frac{1}{2} \Rightarrow r_1 = 30^\circ$
3. Grazing emergence: $r_2 = C = 45^\circ$ (since $\sin C = \frac{1}{\sqrt{2}}$). Prism angle $A = r_1 + r_2 = 75^\circ$.
4. Angles of the triangle: $\theta = 180^\circ - 45^\circ - 75^\circ = 60^\circ$
5. So the answer is (c) $60^\circ$.