Bill- I wish I could say that was close, but it's pretty far off.
1. Diffraction (this isn't "refraction") works with fairly thick slits.
2. The wave penetrates even a good conductor to roughly one "skin depth", in this case many atoms thick, not about one atom.
3. The wave isn't absorbed and re-emitted later as fluorescence, but simply scattered. There's generally no frequency shift and no loss of coherence with the directly transmitted wave, unlike the picture you gave.
4. The phenomenon isn't "poorly understood". The basic effect was understood when Young presented his results to the Royal Society in 1803. It's been understood in greater depth since the development of Maxwell's equations in the 1860's. You can derive the entire thing from Maxwell's equations, just given the conductivity and geometry of the slit material.
Here's what puzzles me. On this site we make some mistakes, but we try to stay away from the topics where we're clueless. You represent a very large group of people who choose to answer questions on the Web on topics with which you aren't familiar. Why do you all do it?
(published on 07/20/11)