*- DORIS FANG -* <sfsttj@xxxxxxxxxxxxxxxxxxx> wrote:
> So, what exactly causes diffraction ? I'm not sure I understand
> the reason.
>
To quote Bekefi and Barrett's "Electromagnetic Vibrations, Waves,
and Radiation:
Physically, diffraction comes about because the incident
radiation induces oscillating currents to flow in the edges
of the obstructing body, and as we know, oscillating currents
radiate.
I'm sure that clears it up. Heh.
It's not easy to explain without going into reasonably complicated
math using waves and all that, and that doesn't really explain it
so much as reformulate the confusion. :-/
Intuitively, when light passes around an edge, it tends to bend
outward slightly rather than cutting off cleanly. To picture this,
try putting an object in a moving stream -- you'll see the waves
spread into the area behind the obstruction. That's similar to
what happens to the light. Of course, with wavelengths on the order
of 500 nanometer, the scale of the spreading is somewhat smaller,
but it's the same idea.
joey
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