Bohr Model: Orbits, Speed & Angular Momentum question from MHT CET 2023 (11 May, Shift 1)

Answer: (b)

1. $v \propto \frac{1}{n}$: from $n = 2$ to $n = 1$, $v_1 = 2v_2$.
2. Change relative to the initial speed: $\frac{v_1 - v_2}{v_2}\times100 = 100\%$
3. Change relative to the final speed: $\frac{v_1 - v_2}{v_1}\times100 = 50\%$
4. The key takes the second form: (b) 50%.