I honestly don't know, that is my question as well. However note that we can only perturb the em field in photon sized energy levels, and we can only pick up d

I honestly don't know, that is my question as well. However note that we can only perturb the em field in photon sized energy levels, and we can only pick up disturbances of the em field in photon sized bunches as well. Not sure what this implies for how em field energy is accumulated on electrons in order for us to detect it.