1. The problem statement, all variables and given/known data Hi, I've been unable to find a relevant thread for a question that I've been stuck on for a couple of days now. Here it is; One of the electromagnetic emission lines for a hydrogen atom has wavelength 389nm. Assiming that this is a line from one of the Lyman (nf =1 ), Balmer (nf = 2) or Paschen (nf =3) series, what is the initial principle quantum number associated with the transitions? The Rydberg energy can be assumed to be 13.6eV 2. Relevant equations ΔE=Ry(1/(ni)2 - 1/(nf)2)) Ry=13.6eV This is the formula used to attempt a solution There is another formula in my notes that may be helpful but i do not understand the symbols within it, it is; En,l = -Ry/(n-δl)2 3. The attempt at a solution Using the equation ΔE=Ry(1/(ni)2 - 1/(nf)2)) and then equating this change in energy to the energy of light E=hc/λ. Ry=13.6eV Then I insert various nf 's e.g. nf =1 for Lyman, then i would solve this for ni to see if i get an integer number, indicating that this is correct. I do this for nf =1,2 and 3 and I have never got an integer number leading me to believe my method is incorrect. Any help or insight would be appreciated, Thanks in advance, John.