Transitions, Photon Emission & Excitation question from MHT CET 2025 (22 Apr, Shift 1)

Answer: (b)

1. Emitted frequency $\nu \propto \left(\frac{1}{n_f^2}-\frac{1}{n_i^2}\right)$; emission needs a jump from higher $n$ to lower $n$.
2. (a) and (c) are absorptions. (b) $2\to1$: $1-\frac14 = 0.75$; (d) $6\to2$: $\frac14-\frac1{36} = 0.22$.
3. So the answer is (b) $n=2$ to $n=1$.