Wondering about the particle treatment of light?

[jeebs]

This question might not even make sense but here goes, it's is about the particle nature of light. As I understand it we can take a sine wave extending throughout all space and add to it others of different wavelength, and we see the the phase differences causing the amplitude to decrease as we look "along" the wave - we get a wavepacket. Is this what a photon is? A localized little bit of electromagnetic wave? If it is, then how do we get photns produced from electron transitions in atoms that only allow 1 very specific energy change/photon wavelength?
If we have a stream of photons of the same wavelength and nothing like a wavepacket is involved, how do we know where to draw the line between where one photon begins and the preious one ends? Like is it just one continuous sine wave - how is it divided up? Does some uncertainty principle effect come into play here where we can't really say where the edge of the photon is or something?

Does it even make sense to try and force a description of a particle out of a wave?

 

[jtbell]

Is this what a photon is? A localized little bit of electromagnetic wave?

No, a photon is not a localized wave packet of the (classical) electric and magnetic fields (E and B). The connection between the photons of quantum electrodynamics on one hand, and the classical E and B fields on the other hand, is complicated and subtle. Also, photons are fundamentally defined in terms of energy, not in terms of position, and they become very "slippery" when you try to pin them down spatially (in terms of position or spatial size).

People have posted about this connection before, but I can't manage to turn up any of those posts via the forum search. Maybe somebody will point us in the right direction.