On Oct 14, 2010, at 7:40 AM, Ed Pozharski wrote: > On Thu, 2010-10-14 at 08:41 +0200, Tim Gruene wrote: >> This sounds as though you are saying that a single photon interacts >> with several >> electrons to give rise to a reflection. > > Not only with several - it shouldn't be much of an exaggeration to say > that the photon senses all the electrons in the Universe as it travels > between the source and detector. Once it hits detector, it's trajectory > magically collapses into a specific one. Quantum physics is undeniably > crazy stuff :) > > Cheers, > > Ed.
Less ephemerally, the photon scatters from every scattering center in the crystal lattice. Under these (incoherent scattering) experimental conditions, it is my understanding that the individual photon only interferes with itself. The "quantum weirdness" creeps in from the fact that the wave describing the scattering is spherically symmetric, sampled by the reciprocal lattice. But if a photon is a particle, and you were to do a single photon experiment, the particle of light can only wind up in one of the diffraction spot locations, but the diffracted wave determines the propensity of the photon to wind up in that location. It is basically the generalization of the single photon double-split "paradox." I've found the headaches start to go away if you don't take the "duality" part of wave-particle duality too seriously. -- Bill
