1. The problem statement, all variables and given/known data Where does a electron emit or absorb radiation? 2. Relevant equations L=mvr=nh (h is diracs constant) (lamda)=(lamda)'(n1^2/n1^2-n2^2) hf = En1 - En2 3. The attempt at a solution I know that in a stationary state an electron cannot emit EM waves, but that if it shifts down the difference between the two goes into energy for EM waves. So does this happen for upward shifts, like if you were at n=1 and went to the first excitation level n=2 for hydrogen would that work as well? Also what excactly is a stationary state is it the level like n=2,3,4 and so on, which is what I assume. Furthermore at the ground state n=1 is any light emitted I would think not because n1=n2 and (lamda) = (lamda)'(n1^2/n1^2-n2^2) you would get a division by zero and the equation would fail which would not permit any light. (Also (lamda)' is the wavelength limit in the equation given).