Answer
If the electron de-excites back to its ground state $(n=1)$ from its third excited state $(n=4)$, there are four possible ways by which it de-excites to ground state. The four possible ways in the form of energy-level diagram are given in the attached figure.
Work Step by Step
If the electron de-excites back to its ground state $(n=1)$ from its third excited state $(n=4)$, there are four possible ways by which it de-excites to ground state. The four possible ways in the form of energy-level diagram are given in the attached figure.
