Physics - Modern Physics Question with Solution | TestHub

The speed of electron is given by $v=2.18\times 10^6\times \frac{Z}{n}m{\text{s}}^{-1}$, where, $Z$ is atomic number and $n$ is number of orbit.

Now, for third orbit, ratio of speed of electron is $\frac{v_H}{v_{H{e}^{+}}}=\frac{Z_H}{Z_{H{e}^{+}}}=\frac{1}{2}$

$\Rightarrow \frac{v_{H{e}^{+}}}{v_H}=\frac{2}{1}$