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I am struggling to understand the concept of a "light wave" From what I understand, when a charged particle accelerates, it creates a disturbance in electromagnetic field that travels through space. Is a photon a single oscillation then? Often times we are shown "light waves" being created by something that is continuously oscillating, so is each oscillation its own photon? The graphics I've seen of light waves often show many many sinusoidal oscillations in the E and B field, is this one photon as it moves through time or is this many disturbances in space?

Basically trying to visualize what happens when a photon is created. I feel comfortable with the idea of oscillating electric and magnetic fields but can't quite rap my head around whether a photon is a single piece of energy or the composition of many oscillations? Does this oscillation create a disturbance that moves in a single direction (perpendicular to direction of acceleration) or all directions (like a pebble dropped into a pond?) Apologies if these questions are a bit convoluted, struggling to rap my head around what's happening.

Thanks so much!


marked as duplicate by John Rennie, honeste_vivere, Jon Custer, M. Enns, Yashas Aug 13 '17 at 15:55

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  • $\begingroup$ It sounds like you're thinking of each single crest and trough as a single photon. That is not correct. But is that your confusion? $\endgroup$ – AHusain Aug 12 '17 at 0:34
  • $\begingroup$ I think so. I am imagining if you were to create waves in rope through continuous oscillation of your hand, there would be many waves in that rope after a while. I'm assuming that a photon would be the EM equivalent of a single wave in that rope? Aren't most of the depictions of EM waves position v. amplitude of E and B field graphs (astronomy.swin.edu.au/cms/cpg15x/albums/userpics/…) and so I am confused whether this picture is showing ONE photon or a series of photons. $\endgroup$ – GThyer Aug 13 '17 at 18:33
  • $\begingroup$ physics.stackexchange.com/a/90657/166178 This helped! $\endgroup$ – GThyer Aug 13 '17 at 18:37

Regarding the EM-fields--I'm going to say the fields just are what they are, and any region where Poynting Vector ($\vec{S} = \vec{E} \times \vec{H}$) generally points in the same direction and falls off no faster than distance-squared: that's a propagating wave.

Regarding photons, without getting into Second Quantization and all that: consider them analogous to phonons in a crystal. The atoms in the crystal vibrate, and the phonon is a collective excitation with frequency and quantized energies that behaves like a (quasi)particle. Likewise, the photon emerges from excitations of the EM field.


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