>
> "...the single photon nevertheless diffracts off many molecules…"
vs.
>
> ... "many photons interfere to produce diffraction pattern" approach
>
Hi Jacob:
This really gets to the essence of the problem. Except in rare instances, a photon only interferes with itself, so the “many photons interfere” approach isn’t really an accurate explanation. Even if one photon goes through the crystal every 10 min (as when collecting data at Daresbury), you will still eventually accumulate the same diffraction pattern.
In addition to Feynman’s very readable QED book, may I recommend another? It is Karl Popper’s Quantum Theory and the Schism in Physics.
http://www.book-info.com/isbn/0-415-09112-8.htm
He argues for an objectivist interpretation of quantum entities, and makes a convincing case. It is a very natural interpretation, at least from a physical chemist’s point of view. We’ve always been taught to think in terms of atomic and molecular orbitals being objectively real entities that can interfere constructively or destructively with one another, whether or not they are actually occupied by electrons, and it is the most straightforward way to understand how it is that a bond can form between two atoms. It works the same way for possible trajectories of photons (or electrons) in a crystal diffraction experiment. His main concern was to offer a rational alternative to mystical and subjectivist interpretations, (i.e., the kind that rake in lots of money from people who believe crystals have healing energy and don’t like to vaccinate their children).
Friday came early this week.
All the best,
Bill
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