Light obeys the particle wave theory. This has always confused me. I understand the mechanism of the wave according to Maxwell theory. But, I run into problems when I think about the photon. How does it propagate? If I have a single photon moving through space, what does it mean? I mean, surely electric and magnetic fields cant only exist at one point helping each other move forward right? If light is electromagnetic, how is a photon electromagnetic? I don't get it. Or maybe because of the uncertainty principle, and we can approximate the momentum of light (radiation pressure), we have no Idea about its position. So the electric and magnetic field exist over some distance, and this is how electric and magnetic fields interact to push the particle forward?
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Chandrahas, think about a photon like a balloon which moves in one direction and periodically expands and contracts up-down and than left-right. Up-down is the electric field component and left-right the magnetic field component. See the answer in the mentioned by John Rennie question. – HolgerFiedler Feb 04 '17 at 11:22
1 Answers
The photon is a quantum mechanical entity, a point particle in the standard model of particle physics, with mass zero, spin 1 and energy=h$\nu$, where $\nu$ is the frequency of the classical electromagnetic wave that can be built up by numerous such photons.
Quantum field theory describes the behavior of elementary particles as free and in interactions with each other. Free each particle has a solution of the quantum mechanical equation appropriate to it, the fermions the Dirac equation. The photon obeys a quantized form of Maxwell's equation and has a wave function.
QFD is a mathematical model that posits that each elementary particle has a field, represented by the ground state wave function, on which creation and annihilation operators work to generate the wave packets that represent the real particles . You will need courses on these subjects to really understand what is happening.
There exists a photon field, and a real photon propagates on this field by creation and annihilation operators .
This may give you an idea:
This graphic shows a circularly polarized photon beam, the red turning arrow the electric field, is build up by photons that only have a forward and backward spin, correlating with the polarization direction. The real, measurable photons do not have electric and magnetic fields. These exist in their wavefunction, which is complex, but the superposition of innumerable such wavefunctions gives the classical electromagnetic wave's electric and magnetic fields. Once you have studied QED you would understand this link that shows how the quantum fields build up the classical ones.
