Q. The electron in a hydrogen atom makes a transition from $n = n_{1}$to $n = n_{2}$state. The time period of the electron in the initial state is eight times that in the final state. The possible values of $n_{1}$and $n_{2}$ are

A) $n_{1} = 6,\ n_{2} = 2$
B) $n_{1} = 2,\ n_{2} = 1$
C) $n_{1} = 8,\ n_{2} = 2$
D) $n_{1} = 4,\ n_{2} = 2$
Explanation

(b) According to Kepler’s 3rd law.
$T^{2} \propto r^{3}$
$\therefore\ \frac{T_{1}}{T_{2}} = \left( \frac{r_{1}}{r_{2}} \right)^{3/2} = 8$
$\frac{r_{1}}{r_{2}} = 8^{2/3} = 4$
According to Bohr atom model, $r \propto n^{2}$
$\therefore\ \frac{n_{1}^{2}}{n_{2}^{2}} = \frac{r_{1}}{r_{2}} = 4;\ \frac{n_{1}}{n_{2}} = 2$
If $n_{1} = 2$, then $n_{2} = 1$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

Want more practice?
Practice Nuclei MCQs