I've been thinking of 2 point charges separated by some distance in static equilibrium. When one charge is moved from rest, the EM field would change the way it looks at the location of the other point charge. This "changing in the looks" of the EM field as I understand propagates from the first charge at the speed of light and constitutes an EM wave. This is easy to see using a computer simulation that allows dragging charges around. When the change in the EM field reaches the other point charge it accelerates, trying to restore equilibrium. So, I know about cases where an excited atom returns to its ground state and how to calculate the frequency and wavelength of the emitted photon. I'm wondering how I might do that with the somewhat unreal situation above. Could I just consider the work done on the second charge to be equal to the light's energy, then divide by Planck's constant to get frequency (if both charges had charge e)? Thanks.