Question

Frequency of revolution of an electron revolving in nth orbit of H-atom is proportional to

• A. $n \,independent\, of\, n$
• B. $\frac{1}{n^2}$
• C. $\frac{1}{n^3}$
• D. n

Answer 1

Answer: (C)

$\frac{1}{n^3}$

Answer 2

Time period of revolution, $T=\frac{2 \pi r}{v}$
Frequency of revolution , $f=\frac{v}{2 \pi r}$
$v \propto\frac{1}{n} r \propto n^{2}$ and hence $f \propto\frac{1}{n^{3}}$