I know that if the intensity of a light beam with of a certain frequency varies it means the number of photons the light beam is composed of varies and not the individual photons energy. That would mean the E and B field amplitudes vary. This would mean that that the amplitudes of the E and B fields are given by the number of photons in the wave. However, I can also think that within the wave in the area where there is an E field maximum amplitude there are more photons which I think doesn't make sense. When two EM waves overlap (same phase) the E and B fields add up. But the number of photons is preserved (they don't merge) because if in a pulse of light the photons energy is preserved the number of photons,!carrying the smallest quantum of energy, will increase. That can mean that there are two types of amplitudes. One that is discrete and gives the energy of the photon and the other that gives the number of the photons. In classical physics and when using radio waves they seem to mean the same thing.