Quote:
Originally Posted by CraigD
Just the sort of semantic we’re here to discuss! 
As far as I know – and I could well know wrongly - the Faraday effect can only occur when light passes through a non-vacuum medium – that is, a volume with non-zero rest mass particles in it. I don’t believe a beam of polarized light has its polarization rotated if it passes through a magnetic field in vacuum.
So it’s not an example photons interacting with other photons – which I understand is forbidden – but magnetic interaction photons interacting with fermions (usually electrons), which interact with EM radiation photons. In practical terms, true vacuums don’t exist enough to worry about – interstellar space, for example, has at least 2000 electrons/m  , so magneto-optical effects like the Faraday effect happen effectively everywhere - but for understanding fundamental interactions, the distinction is, I think, critical.
I don’t know how to describe light polarization effects – Faraday or others – in terms of photon-fermion interactions. If someone can, I’d greatly appreciate it – it’s puzzled me for a long time.  |
thank you craig, i think it is important to note that the farady effect is a result of the magnetic field acting on an electron, and not on a photon.
i don't fully understand the way fermoins work but i do know that they all have half integer spin so if an electron absorbs a photon, then rotates around their its axis due to the spin of the fermion, and then re-emit a photon, that photon's plane of polatization will move in a clock wize or anty clock wize direction.
what 'spin' really is, is something that i am still learning about but it can be considered to be an actual spin of the electron according to wiki.
"spins obey the same mathematical laws as do quantized angular momenta."
...i can't post links yet
, it's the wiki page titled "Spin_(physics)"
the above mentioned page from wiki about the farady effect has a good diagram that shows how it works. it's important to remmember that the vector of a magnetic field point to the north pole, while it's spin is around the south-north axis !
i hope this will shed some light on the topic. i think that in order to properly understand the whole magnet thing i will have no choice but to study maxwell's equations... hmm
