Question

An electron of H-atom de-excites from energy level $n_1=2$ to $n_2=1$ and the emitted photon is incident on $H{e}^{+}$ ions in ground and first excited state. Which of following transition is possible.

• A. $n=1$ to $n=4$
• B. $n=2$ to $n=4$
• C. $n=2$ to $n=3$
• D. $n=1$ to $n=3$

Answer 1

Answer: (B)

$n=2$ to $n=4$

$E=13.6\times 1(\frac{1}{1^2}-\frac{1}{2^2})$

$\Rightarrow 10.2eV$

for He+in $n=2$
$10.2eV=13.6\times 4(\frac{1}{2^2}-\frac{1}{n^2})$
$\Rightarrow n=4$