I've been puzzling over the two-slit experiment. There's an alternate setup where you use lasers and prisms. [A laser beam is split with a half-silvered mirror/prism. Photons take one path or the other and hit one of two detectors. We arbitrarily insert a converging mirror/prism near the end, and instead of the photons choosing a path, we get an interference pattern - the photons must have taken both paths. Thus, wave-article duality.] It seems to me that the mystery lies - not in the outcome at the detectors - but at the first mirror. How do photons bounce off the mirror at the correct angle? A rubber ball bounces off an angled surface because it impacts as an area. The ball "knows" what the surface is like and elastic distortion takes care of the rest. But in the subatomic world, the finest of mirrors is a collection of atoms that are alomost entirely empty space. As a particle, the photon is going to encounter - well - most likely nothing. I can see it encountering one atom at most, but never more than one. It cannot possibly "know" the arrangements of other atoms, and therefore "know" it should bounce at the right angle. So, its got to be the wave property that encounters the wall of atoms. OK. So the waveform of a single photon must be, at a minimum, wider than two atoms' distance. It must be much wider than merely two, or small perturbations in each atom would send photons reflecting at a range of angles. So, how "wide" is a photon wave, what's its amplitude? Wait a minute, amplitude is associated with strength. but when you brighten a beam of light, you don't increase the amplitude, you merely send more photons. Do individual photons have a property of amplitude? Is there a way a photon's amplitude can be changed? Or is amplitude is direct function of frequency? Higher freq photons will interact with the mirror better because they have a wider wavefront (or worse because its narrower)? Sure - that's why glass mirrors don't deflect X-rays. The X-rays have a narrow wavefront, too narrow to notice the wall of giant atoms. Wait, wouldn't that suggest that lower frequency photons would be *more* easily stopped by glass? Shouldn't glass deflect radio waves? But I digress... Do I have it right that the *amplitude* of a photon's wave is the property that allows it to reflect off a mirror/prism at an angle? Can someone enlighten me?