What hydrogen atom transitions represent emission of the longest wavelength photon?

Wavelength has inverse relationship with its energy. The shorter the wavelength, the higher the energy.

Complete question was:

Which of the following transitions (in a hydrogen atom) represent emission of the longest wavelength photon? n = 1 to n = 2 n = 3 to n = 1

n = 3 to n = 4

n = 4 to n = 2

n = 5 to n = 4

The longest wavelength photon is n = 5 to n = 4. As I stated above, the wavelength and energy has inverse relationship. The longest wavelength has the lowest energy.