1. The problem statement, all variables and given/known data Not sure if this belongs in the 'Advanced' section so apologies if it does not. I am using a monochromator to measure spectrum lines from a rubidium lamp. From the data (wavelength of spectral lines plus transition number 'n') I am asked to use a graphical method to calculate both the Rydberg constant and the correction factor Δ due to the penetration of the outer valence electron into the inner electron cloud. 2. Relevant equations 1/λ = 1/λ∞ - R/(n + Δ2) where λ is the wavelength; R is the Rydberg constant; λ∞ is the series limit (which I presume to be the highest wavelength at which transition can occur?) n is transition number and Δ is the correction factor. 3. The attempt at a solution I am aware that by 'linearising' the equation ( ie. putting it into the form y = mx+c) I can find the Rydberg constant as the gradient of the line of best fit. I've used this method before in determining the Rydberg constant from Balmer lines of hydrogen. The problem this time is that there are two unknowns, and my efforts to find the constant plus correction factor have not been successful. I'm not sure how to go about this - any advice much appreciated. Cheers!