The transition with the greatest distance is 5p → 1s, which is n = 5 going to n = 1. This means this transition also has the largest energy and frequency. Therefore, the electron transition that produces light of the highest frequency in the hydrogen atom is a. 5p → 1s.
Explanation:
The energy requirement order for excitation for different transitions is as follows. n→∏* transition requires lowest energy while σ→σ* requires highest amount of energy
