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techmind wrote something which set me thinking.If photons really are like little squiggles of em wave, then their electric and magnetic field vectors must be of a specific amplitude so that the total energy is hf.If you take an non polarised source of one frequency of light, then all the photons will be identical in every respect apart from the plane of their E and H fields.If you then pass the stream of photons through a polarising filter, what does this polariser actually do?The photons that emerge must all have the same magnitude of E field as before. If it just selected those photons which started off with the E field parallel with its selected plane then you would only get a very few coming through (an infinitesimal fraction of the incoming stream). So that can't be right.We know that a polariser lets just half of the power through it and that the polarisation is in a particular plane. Has the polariser just picked half of the photons and twisted their polarisation to be all in one plane?Follow this polariser with a further polariser with its plane at 60 degrees to the first and will produce half brightness. Again, this polariser must have let through a selected half of the photons ( which ones and why?) and their plane must have been rotated also.Treating this problem as a wave problem there is no problem at all. You just resolve E fields and discard one of the orthogonal components - resulting in half the power and a particular polarisation. If you wait until then to treat the light as a shower of photons interacting with the detector, you can predict the result with no nasty questions needing to be asked.Then, look at radio waves. You can produce any polarisation you like (plane, circular, elliptical) using a combination of waves produced by two totally independent transmitters (just at the same frequency and phase locked) feeding two crossed dipoles. Take the simplest example of the two transmitters being in phase and producing a slant linear polarisation. The 'photons' produced by each dipole will be only oriented on one plane - parallel to each dipole. How, then, can you suddenly get photons produced with an arbitrary polarisation angle out in the space in front of the two dipoles?Remember, anything which applies to light must apply to radio waves and vice versa.
The stimulated emission concept is quite interesting.Now we know that inherently the energy "gap" in the excited-state atom is perfectly matched to the rest of the laser-radiation in the cavity.We also know that the excited state has to be relatively "long lived" (metastable or whatever) to as to "hang around" long enough to be taken to the ground state predominantly by stimulated emission rather than random emission (sorry I can't think of the proper word). The fact that it "hangs around" could be interpreted/considered as some kind of energy potential-barrier.So if the excited atom momentarily "borrows" some energy from a passing "photon" then it can return to the ground-state.Buuuut... I said before the energy gap is "perfectly matched", which might imply a concept a bit like a high-Q resonant system has some relevance? ... something that would couple to an EM wave of the precisely correct frequency...? And if this was the case you might expect the stimulated "photon" to be phase-matched and polarisation-aligned to the stimulating "photon"?A bit handwavy I'm afraid - tis late at night, plus a decade or more since I studies undergrad photonics. What do you think? sophiecentaur?
If you then pass the stream of photons through a polarising filter, what does this polariser actually do?
I'm quite attracted to the concept of a photon as a waveicle - some short burst of a classical wave. Presumably quantisation happens in some way, but let's leave that for a moment. Of course this could just be self-delusional wishful thinking.
It seems obvious to me that "photon" is the name that we give to the smallest possible energy-time we can get from a specific electromagnetic wave. Most of them happen when an electron moves form one energy state to another. It makes one transition. It signals that transition by radiating and electric field and a magnetic field that are in phase with each other. The most simple signal would be one cycle of energy. Observation indicates that the cycle of energy exists as a point surrounded by the fields. The fields diminish away from the point. The fields represent a probability amplitude that the point of action may occur in a spacial area away from the path of the point.I don't see anyone here agreeing with that concept, but it solves many problems for me.
The problem with the concept you describe is that a single, isolated, cycle of a waveform is not analysed as a single frequency.
Interesting question.Dunno if this helps or not, but in the n-dimensional model I've been playing with, photons come out as a pair of two-dimensional objects, one following the other. Having 'width' and 'height', but no 'length', they have orientation about their axis of movement. Two, one following the other, are required to account for wavelength and the phenomenon of frequency shifting, whilst also accounting for circular polarisation by having different orientations. This is all pretty irrelevant to the models you're already working with though, and the model is still incomplete.
So, are we saying that the polarisation is not relevant to the photon? Are the photons not to be regarded as existing in the wave? How do the +/-1 spins fit in? It may help me to square things.
Can we satisfy all the known results by assuming the polarizer passes photons with a statistical probability proportional to the magnitude of the component of the photon polarisation parallel to the polariser polarisation? ie proportional to the cosine of the angle between the polariser and photon polarisation?
Quote from: techmindThe problem with the concept you describe is that a single, isolated, cycle of a waveform is not analysed as a single frequency.True; a single cycle can not be analysed as a frequency. However we can know that it may exist. Planck's constant represents some number of cycles of electromagnetic energy. That number needs to be 1 in order for things to make sense.
jpthat seems fair enough - the 'resolving' is done, not with the E field but with the statistics of numbers of photons.Meanwhile, how does this help with ascertaining how big a region the photon actually has an influence? (i.e. its size)
The appeal of the single wiggle is that we can then construct a particle of matter from it by looping it around so that the front catches the back and forms a resonant circle. It is held in place by positive feedback and resonance  I was trying to write a computer simulation of a neutron when I discovered that one cycle was necessary to develop the charge on a particle. One cycle in a circle places the same polarity on the outside of the circle all the way around.Neutron model:Edit: The positive feedback develops from the electric charge which is caused by the asymmetry of the fields in the bend of the curve. The electric plane is shown; the magnetic plane would extend outward toward the viewer and away down into the screen.The width and height of the fields would extend outward forever. I'm not sure how to make the fields collapse when a photon is absorbed.
Positive feedback, sometimes referred to as "cumulative causation", is a feedback loop system in which the system responds to perturbation in the same direction as the perturbation. In contrast, a system that responds to the perturbation in the opposite direction is called a negative feedback system. These concepts were first recognized as broadly applicable by Norbert Wiener in his 1948 work on cybernetics.