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Re: CD's and CD-ROM's



Bob,
I think the article you want is in The Physics Teacher, Vol. 28,
no. 7 1990, page 484. To get the diffraction greating effect all you need is
a closely spaced periodic structor. Even though the dots are nearly random in
their spacing along the track, the tracks themselves are periodically spaced,
and that is the direction the diffraction takes place. I believe the tract
itself is a spiral like a phonograph record and not concentric rings like a
floppy disk, but this shous
floppy disk, but this should not effect the results.
I have not done the experiment myself but I have wondered if the inter
mitent nature of the spots would lead to Rolland Goasts in the spectrum producedby such a grating. The other sources of noise may be too great but it is worth
looking for.
Gary