In a large sample of hydrogen atoms, electrons are initially in the third excited state. As they de-

Question

In a large sample of hydrogen atoms, electrons are initially in the third excited state. As they de-excite to the ground state, how many distinct spectral lines are observed that belong exclusively to the Balmer series?

Professor PC Thomas Classes · Answer

(a) : The third excited state corresponds to the principal quantum number $n = 4$. The Balmer series consists of transitions that terminate at $n = 2$. From the $n=4$ state, the possible transitions terminating at $n=2$ are $4 	o 2$ and $3 	o 2$. Therefore, exactly 2 distinct spectral lines belonging to the Balmer series will be observed.