I've seen two versions of the same formula: one is v = R(1/n1^2 -1/n2^2). The other is 1/wavelength = R(1/n1^2 -1/n2^2). I was just wondering which of these two equations is correct and what's its main use is for
I've seen the equation written both ways too and I think that both are correct. This formula is mainly used to determine the wavelength of light emitted by an electron moving between the energy levels of an atom.
Depending on what is given, it can be used to determine the frequency, wavelength, or the other energy level. I don't know for sure whether or not it will be on the 2nd test, but I think it is likely that it will be.