What is the longest wavelength light capable of ionizing a hydrogen atom in the n = 4 state?

i know that Solve h c/L = (Rydberg)/6^2 for L
something along those lines... but what am i solving for and what is c and h?

2 answers

c is the speed of light. L is wavelength. YOu really ought to get familiar with equations you are using. Anyone can plug formulas.
so i would do speed of light/(rydberg)/6^2=h?