1. The problem statement, all variables and given/known data part b) Calculate the recoil shift for the emission of the most energetic Lyman line from a free atom of hydrogen. 2. The attempt at a solution My question isn't a physics one per se, I'm stuck on terminology. What is meant by "the most energetic Lyman line"? I'm use to thinking of Lyman series in terms of frequency, and it doesn't seem to make sense to me to try and calculate the energy from frequency in this case. Any thoughts?