Polarization of Electromagnetic Waves: A Quantum Perspective

[fluidistic]

Imagine an unpolarized EM wave going into the z direction. Put a polarizer so that you linearly polarizes the EM wave. I know that the electric field direction of the wave will always be the same. But what about its magnetic field?
Is it possible to affect the magnetic field of an EM wave? Can a wave be polarized electrically and not magnetically, at the same time? Not sure these terms are making sense.

 

[tiny-tim]

hi fluidistic!

the magnetic field is always 90° from the electric field, and it goes through too

i know we always think of a polariser as a grating that only one direction of wave can slip past, but that's misleading: it's purely conventional to describe the direction of a polariser as the direction of the electric field that it let's through: we could equally well have the opposite (well, 90°-osite!) convention

 

[fluidistic]

hi fluidistic!

the magnetic field is always 90° from the electric field, and it goes through too

i know we always think of a polariser as a grating that only one direction of wave can slip past, but that's misleading: it's purely conventional to describe the direction of a polariser as the direction of the electric field that it let's through: we could equally well have the opposite (well, 90°-osite!) convention

Thanks I think I get it.
So if a polarizer affect the E field direction, so will the B field be affected in order to always stay perpendicular to it.
And yes, of course I understand the convention of the direction of a polarizer.
Thank you very much, doubt cleared. (By the way I just found in wikipedia the part

Conventionally, when considering polarization, the electric field vector is described and the magnetic field is ignored since it is perpendicular to the electric field and proportional to it.

which is exactly what you mean.)
I'm happy.

 

[K^2]

You can think of EM wave as being absorbed and re-emitted at every point in space. Forget about vacuum for a moment, and think about EM wave traveling through some linear medium. Oscillating electric field causes the electrons in matter oscillate and becomes absorbed. These oscillating electrons produce a new electromagnetic wave that is emitted.

The interesting bit about polarizer is that it only allows electrons to shift in one direction. Kind of like beads on a wire. So electric field oscillating one way will become absorbed and re-emitted, and field oscillating in a perpendicular direction will not be allowed to pass through. Because it is the electric field that excites the electrons, the direction of magnetic field doesn't really affect anything, and the magnetic field in the newly emitted wave is perpendicular to the direction of the electric field.

So polarizer does effectively polarize both, but it affects the electric field directly.

Note that this is classical picture. If you want to consider QM of polarizers, things become far more interesting.

 

[fluidistic]

You can think of EM wave as being absorbed and re-emitted at every point in space. Forget about vacuum for a moment, and think about EM wave traveling through some linear medium. Oscillating electric field causes the electrons in matter oscillate and becomes absorbed. These oscillating electrons produce a new electromagnetic wave that is emitted.

The interesting bit about polarizer is that it only allows electrons to shift in one direction. Kind of like beads on a wire. So electric field oscillating one way will become absorbed and re-emitted, and field oscillating in a perpendicular direction will not be allowed to pass through. Because it is the electric field that excites the electrons, the direction of magnetic field doesn't really affect anything, and the magnetic field in the newly emitted wave is perpendicular to the direction of the electric field.

So polarizer does effectively polarize both, but it affects the electric field directly.

Note that this is classical picture. If you want to consider QM of polarizers, things become far more interesting.

Thank you very much. That's very informative. If you don't mind, feel free to give me (or us should I say, considering other people interested) links/name of books on the quantum approach of polarizers. Or even a brief comment, anything will do, I'm interested.