Question

In a container, a mixture is prepared by mixing of samples of hydrogen atom, helium ion $\left(H{e}^{+}\right)$ and lithium ion $\left(L{i}^{2+}\right)$. In the sample, all the hydrogen atoms are in $1^{st}$ excited stae and all the $H{e}^{+}$ ions are in third excited state and all the $L{i}^{2+}$ ions are in fifth excited state. Find the total number of spectral lines observed in the emission spectrum of such a sample, when the electrons return back upto the ground state.

Answer 1

But , $(H{)}_{2\to 1}=(H{e}^{+}{)}_{4\to 2}=(L{i}^{2+}{)}_{6\to 3}$ are lines of same energy and so, will overlap each other.
$\therefore$ Total of lines observed = (1+6+15) -2 = 20 lines.