1. The problem statement, all variables and given/known data Make a rough estimate of the ionisation potential of potassium (19) given the following infomation relating to its optical spectrum: wavelength of the first line of the Sharp Series: 1248nm wavelength of the first line of the Principal Series: 767nm wavelength of the first line of the Diffuse Series: 1173nm wavelength of the first line of the Fundamental series: 1516nm speed of light = 2.998 x 10^8 m/s Planck Constant = 6.626 x 10^(-34) Rydberg constant R∞ = 1.097 x 10^7 electronic charge = -1.602 x 10^(-19) 2. Relevant equations I = (Rhc)/((n-δ)^2) 3. The attempt at a solution I have no idea how to go about this at all. I have tried but got nothing.. I was told that δ was a ratio of some sort.. but I don't know what of.. A method of how to go about this would be great and an explanation of why would be handy too.