Question:

The transition from the state n=4 to n=3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from which of the following?

2→1

3→2

5→4

4→2

IR corresponds to the least value of (1/n₁² - 1/n₂²), i.e., from Paschen, Bracket, and Pfund series. Energy of transition is less only in this case.