Isn't linearly polarised light actually chiral when taking the magnetic field into account?
Just looking at the electric field is just 2D and therefore achiral, obviously.
But with the magnetic field included, the mirror image isn't the same right?
Everywhere I look it is written that linearly polarised light is achiral, I'm assuming because usually the magnetic field is disregarded.
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3$\begingroup$ You should think of the magnetic field not as a vector but rather as a bivector, a surface "thing". For a linear polarized wave the electric field vector and the direction of the ray (Poynting vector) forms a plane, the magnetic field as bivector is in that plane not as a vector but rather as "whirl"., see physics.stackexchange.com/questions/410714/… and physics.stackexchange.com/questions/160993/…; no mirror worry now. $\endgroup$– hyportnexCommented Feb 8 at 14:51
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$\begingroup$ Thank you! I don't understand this :( $\endgroup$– JorgeCommented Feb 8 at 15:21
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$\begingroup$ to get a better feeling you should remember that the electric field is associated with a path integral representing work along it. The relevant part of the projection of the E- field on the tangent line to the path. The magnetic B-field is associated with flux through a surface, it is a surface thing, and on that surface it can whirl clock-wise or counter-clockwise in analogy to a vector that can point along a line "up" or "down". A surface "thing" such as a B-field can be represented by a pair of vectors similarly to a volume "thing" that would need three vectors. $\endgroup$– hyportnexCommented Feb 8 at 15:31
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$\begingroup$ Now think of what happens to CW and CCW in a mirror. $\endgroup$– hyportnexCommented Feb 8 at 15:32
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$\begingroup$ WP and also. $\endgroup$– Cosmas ZachosCommented Feb 8 at 15:53
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1 Answer
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The photons of electromagnetic radiation are chiral. And the reason is exactly the one you cite and which is also mentioned in the name - "electromagnetic" radiation. What's more, the photons of electrons all have the same arrangement of electric and magnetic field components. This is easy to prove.
In a radio wave, the electrons are moved back and forth on the antenna rod, emitting vast quantities of polarised photons. Their electric fields are sometimes orientated upwards (for a vertical rod, of course) and sometimes downwards every half period. At the same time, the magnetic fields of the photons are sometimes orientated to the left and sometimes to the right. If this were not the case, we would not be able to build a magnetic antenna as a receiver.
Addition
The electric and magnetic field components of an antenna are emitted perpendicular to each other. The two sketches show the near field of the antenna, in which the two components oscillate offset by 90° in the direction of radiation. It can be seen from the sketches that the position of the two fields can be readjusted according to the right-hand or left-hand rule (which also determines the chirality). Nature has - fortunately - decided that the electrons only emit photons according to the right-hand rule. Otherwise the generation of electricity and radio transmissions would be impossible. Lorentz force and Hall effects would also be impossible.
answered Feb 11 at 5:54