Paragraph: In a mixture of $\mathrm{H}-\mathrm{H}^{+}$gas $\left(\mathrm{He}^{+}\right.$is singly ionised…
Paragraph:
In a mixture of $\mathrm{H}-\mathrm{H}^{+}$gas $\left(\mathrm{He}^{+}\right.$is singly ionised $\mathrm{He}$ atom), $\mathrm{H}$ atoms and $\mathrm{He}^{+}$ions are excited to their respective first excited states. Subsequently, $\mathrm{H}$ atoms transfer their total excitation energy to $\mathrm{He}^{+}$ions (by collisions). Assume that the Bohr model of atom is exactly valid.Question:
The quantum number $n$ of the state finally populated in $\mathrm{He}^{+}$ions is
2
3
4
5
Solution
Energy given by $\mathrm{H}$-atom in transition from $n=2$ to $n=1$ is equal to energy taken by $\mathrm{He}^{+}$ atom in transition from $n=2$ to $n=4$.
$\therefore$ correct option is (c).
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