chemical principles edition 6 problem 1.13

[Kassidy Tran 1E]

I'm a bit confused on this problem:
Use the Rydberg formula for atomic hydrogen to calculate the wavelength of radiation generated by the transition from n = 4 to n = 2.
In this problem, would 4 be considered n1 and 2 be n2? Or should it be the other way around to avoid any negative values?

[Mindy Kim 4C]

When finding the wavelength of radiation emitted by a hydrogen atom in a transition from one energy level to another, the initial or starting energy level is n1 and the final energy level is n2. Therefore, n1=4 and n2=2. Your change in energy will end up being negative because when an electron moves to a lower energy level, it emits energy. However, when calculating wavelength, you make this value positive as the loss in energy is converted to photons. There cannot be a negative wavelength, so making the value from the Rydberg's formula positive ensures you get a positive wavelength as your final answer.