This started out talking photons, then moved to EM Waves. Its simpler to 'pick-one' for any particular problem. Personally, I don't believe photons exist at least until matter gets in the way. Once a wave is present, you can't reduce or destroy its energy with another wave.. but you can...
I was taught that photons ( non-ionizing at least) never interact. So Its really bugging me that most info on faraday effect invokes B field as the cause of ( for example) rotation effects. Since EM-waves (IE Photons) themselves propagate a (oscillating) Magnetic field through infinite space...
What a great disucssion... I can't help adding my opinion..
Light THeory, like all things, is being explained by humans.
This means we are forced to try to use existing familiar concepts.
Unfortunately, humans arent very good at understanding things that don't have an easy analogy with some...