Question

The period of revolution of an electron revolving in $n^{th}$ orbit of $H$-atom is proportional to

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

Answer 1

Answer: (C)

$n^3$

Answer 2

As we know that time period of revolution of an electron is
$T =2 \pi r / v$,
And $r \propto n^{2} / Z^{2}$ and $v \propto Z / n$
$\therefore T \propto n ^{3} / Z ^{2}$ and for $H$ -atom
$Z =1, T \propto n ^{3}$