Mike wrote:
> 
> I have a book that talks about diffraction gratings.  Says a typical one
> has 14,000 to 15,000 rulings per inch and that for maximum efficiency
> the seperation of them should be on the order of 1/50,000 inch, or about
> the wavelength of light.
> 
> I would think aliasing would be a problem. ;)

Well, that's because of what they are designed to do.  One big use is in
spectroscopy where they want a nice reliable, computable relationship
between the angle of deflection and wavelength.  Prisms don't cut it
because the dispersion isn't a linear (or anything else) function of
wavelength.  Diffraction off that sort of grating is very well defined
though.  But you don't need a grating.  Find your local gadget freak and
try to borrow their laser pointer.  While you're at it, yank one of
their hairs out.  Now find a white wall and blast the laser at the wall
and stick the hair in the way.  You get the main spot from the pointer,
but also some nifty satelite spots on either side.  Or, try flashing it
off a CD and see how many spots you get.  That's the sort of thing I'm
talking about.  

My guess is that it would have to deal with things in two ways. 
Diffraction due to the shape of some small, individual object (hair,
pinhole, etc.) and diffraction due to a grating type texture that would
treat things like the opalescence does now.

-- 
Carl Bartels, Department of Chemsitry, Mcgill University, to reply to
me,
just kill a and 5 from the email name, Montreal, QC, cAnAdA

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