What is the frequency of a Hydrogen photon resulting from the transition of n = 7 → n = 1 ?

Answer 1

I would do this
1/wavelength = R(1/1^2 - 1/7^2)
Then convert wavelength to frequency from
c = frequency x wavelength.
R = Rydberg constant. I can look that up if you don't have it.

Answer 2

Thanks so much.