For which of the following transitions does the light emitted have the longest wavelength?

Question

For which of the following transitions does the light emitted have the longest wavelength?

Answer 1

The longest wavelength would be associated with the lowest energy. The lowest energy would be associated with the smallest transition. You didn't provide any choices, so just pick the one that has the smallest transition. For example 3 to 2 would be smaller than 3 to 1.