Prism, Dispersion & Scattering question from JEE Main 2026 (28 Jan, Shift 2)

Answer: (b)

1. With $\delta_m = A$: $n = \dfrac{\sin A}{\sin\frac{A}{2}} = 2\cos\frac{A}{2}$.
2. Angle of incidence $i = \frac{A+\delta_m}{2} = A$ must be at most $90^\circ$, so $0 < A \le 90^\circ$.
3. Then $\cos\frac{A}{2}$ lies between $\frac{1}{\sqrt{2}}$ and 1, so $\sqrt{2} \le n < 2$.
4. So the answer is (b) $\sqrt{2} < n < 2$.