Just trying to plug another hole in my brain:
Light bends when it closely passes an object.
What is actually happening to make that occur?
Forget I asked; I see it’s already been answered in this thread:
http://boards.straightdope.com/sdmb/showthread.php?threadid=116751
(which was the one that started me wondering about it in the first place).
Simplest explanation: Light does not follow straight line paths at all. In fact, it follows all paths. With no edge nearby, it appears to follow a straight line path because along any other direction nearby waves destructively interfere with each other. But along the straight line direction only, nearby waves do not differ by enough in wavelength to interfere with each other. That is why the long wavelengths diffract much more. The same thing is true with mirrors. It is only at a stationary point in the distance (that is usually the least distance, but with a suitably curved mirror could also be the greatest) that you get reflection. But if you carefully cut out lines in a mirror so that nearby waves are absorbed instead, you will no interference (at a selected wavelength) and get reflection all along the mirror. This is what a diffraction grating is all about. Note that this is totally at odds with a corpuscular theory of light. In fact, it was diffraction that lead people to abandon it. But there were other expermiments that seemed to show the contrary. Now if only I understood that…