Post AtQNxRz0b110R7NOFc by wistahe@im-in.space
(DIR) More posts by wistahe@im-in.space
(DIR) Post #AtPVLYJTDZ1jXWQX6u by wistahe@im-in.space
2025-04-24T08:11:26Z
0 likes, 0 repeats
I feel like it's pretty confusing for a new physics student when they learn about light in undergrad. Like a photon is a wave in two separate ways! It's a wave in the sense that it's a moving point with a changing phase for its electric and magnetic fields at that point. But it's also a wave in the same way that every particle is a wave, it is represented by a probability wave where the exact orientation of propagating phases cannot be measured and only the differences matter between them. It has two phases, one whose value has physical significance and the other where it doesn't, and they are not at all the same thing! And what we often refer to as light aren't photons, but phase planes which are planes of photons where all photons in a plane have constant electromagnetic phase. Correct me if I've gotten anything wrong.
(DIR) Post #AtPVLZpPaIAgEsNYXI by wolf480pl@mstdn.io
2025-04-24T08:27:19Z
0 likes, 0 repeats
@wistahe wait what? There's a second non-EM wave associated with photons that is different?Does it lead to different interference patterns than the EM wave?
(DIR) Post #AtQNxRz0b110R7NOFc by wistahe@im-in.space
2025-04-24T18:39:12Z
0 likes, 0 repeats
@wolf480pl It's just the probability amplitude from quantum mechanics. Like how all particle have a wave associated with them. If you were to shoot one photon at a time through a double slit, you should see that interference pattern. The interference pattern in classical EM is not due to individual photons, but the EM field of many different photons at the same time.
(DIR) Post #AtQO7nm6Qg9mv0H9Ga by wolf480pl@mstdn.io
2025-04-24T18:41:08Z
0 likes, 0 repeats
@wistahe sure butdo they end up being two different interference patterns?If I had a dial that changes how many photons per second I'm shooting at a double slit, am I going to get some interpolation between the two patterns?
(DIR) Post #AtQOzUxCca4MBS4WFU by wistahe@im-in.space
2025-04-24T18:50:48Z
0 likes, 0 repeats
@wolf480pl That's a really interesting question! But if I understand things correctly, then yes you can. Technically what causes the wave dispersion in classical waves is the medium it travels through. Light that hits say an air molecule will be remitted in a random spherical direction. It's just that with many photons, phases cancel out so we still see wavefronts. If the medium was vacuum, with classical EM waves the two slits should just produce two beams of light that do not interfere. But in quantum mechanics, with one particle at a time, you would still see an interference pattern. So in a vacuum, the intensity would shift from an interference pattern to just two beams.
(DIR) Post #AtQPPW7wsi57LsVNRI by wolf480pl@mstdn.io
2025-04-24T18:55:33Z
0 likes, 0 repeats
@wistahe wtf?No, no fuckin way.If this was the case, we could easily get around the diffraction limit of telescopes and microscopes by just putting them in the same vacuum that the observed object is in.
(DIR) Post #AtRGN0wr806Ddy0ZDk by wistahe@im-in.space
2025-04-25T04:48:53Z
0 likes, 0 repeats
@wolf480pl Wait, I was very wrong. Photons do not have an EM phase. In fact, it wouldn't make any sense because that would mean they change over time which they can't since they move at the speed of light. EM wave phase is a collective property of the photons.Does the inference pattern from single photons match the interference pattern of a classical beam? It must, right?
(DIR) Post #AtROvGolQnyELD4JwO by wolf480pl@mstdn.io
2025-04-25T06:24:47Z
0 likes, 0 repeats
@wistahe I thought photon was just a quasiparticle arising from the quantized EM field. Would that be the same as EM phase being a collective property of photons, or is it sth different?
(DIR) Post #AtRXHVsytA1P4t9sum by wistahe@im-in.space
2025-04-25T07:58:24Z
0 likes, 0 repeats
@wolf480pl I don't really know enough to answer the question at the moment confidently. I'm learning about spinors and tensor calculus at the moment, so I haven't gotten to quantum field theory. But as I understand it, EM phase is a collective property of photons. Individual photons do not have an EM phase, but their wavefunctions do interact in order to produce one.What I don't understand though is that the electric field is a vector field. As I understand it, the phase of an EM wave is very much physical since it determines the direction of that vector. But the exact angles of wavefunction phases do not matter and only the differences matter, so how do they determine where the electric field vector points?Is it that light is always in a superposition between spin up and spin down, but when we put photons together their wavefunctions interfere giving us the electric field vector as a probability weighted average of their spins?