Question

Photons corresponding to the $10\to 2$ transition of $H{e}^{+}$ ion sample is used to excite the $H$-atom sample in ground state. If electrons make transition up to ground state after excitation in $H$-atom sample, then find out the maximum number of spectral lines produced in the infrared region.

Answer 1

Answer: 3

$10\to 2$ transition of $H{e}^{+}$will cause $1\to 5$ transition in $H$-atom.
$\therefore$ maximum number of spectral line
$=\frac{5(5-1)}{2}=10$
$\therefore$ number of lines in infrared region
$=10-4-3=3$.