Date: Thu, 21 Mar 2002 08:59:53 -0700

Author: Jerry DiMarco

Subject: Re: POISSON'S (ARAGO'S) SPOT

Post:

Another neat demo to do is the inverse of Poisson's spot, a dark spot
in the middle of a bright area. I can't find this one in the DCS although
6C20.30 - Airy diffraction rings seems similar. The Pasco optics kit also
contains a variable aperture that works well for this demo. Just put it in
front of an expanded laser beam and gradually close the iris. You can
watch the diffraction pattern developing, then at minimum aperture a dark
spot appears in the center. It is especially nice and sharp with a
spatially filtered beam...

Jerry


At 3/15/2002 02:45 PM, you wrote:
>...Yes, we are talking about the bright spot in the center of the shadow...
> ....Doug J.

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