I was looking for a frequency by calculating the wavelength, and I found the answer. However, I have no idea where I came up with one of the values! my notes say: wavelength = Planck Constant / (proton mass * velocity) My values: 1.9078e-21 m = 6.63e-034 / (2.81e-8 * 1.236e-5) The velocity is equal to longest wavelength of the electromagnetic radiation emitted by the hydrogen atom undergoing a transition from the n = 7 level, shown in m/s. The Planck Constant is what it is. But what was I thinking when I came up with the mass of a proton as 2.81e-8?! Here's the thing THE NUMBER WORKS. And when I came up with that one, I was like, "Okay, we'll just call that 'proton mass' for now and see what happens." I'm sure it had something to do with charge and/or angular momentum. Does anyone know what I was thinking?! Thanks!