1. The problem statement, all variables and given/known data I've been given 2 values for the potential, 10.2 and 12.1V, I have to find the principle quantum numbers of which have been excited. 3. The attempt at a solution I know En= -13.6/n^2 From there I'm stuck, I know it should go up in 4.9v, but 10.2 and 12.1 aren't multiples of either! If it were, I could work out how many multiples they were, and that would be n.