On Friday 24 August 2007 12:22, Michel Fodje wrote: > 1. In every description of Braggs' law I've seen, the in-coming waves > have to be in phase. Why is that? Given that the sources used for > diffraction studies are mostly non-coherent.
Think of Bragg's Law as explaining what happens to a single photon that is probabilistically scattered by every atom in the lattice. It's perfectly coherent with itself. This idea should be no stranger than textbook illustrations of the result of sending a single particle through a narrow slit or pinhole. The interference effects follow the expected predictions even for illumination by one particle at a time. -- Ethan A Merritt
