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Poisson/Arago's spot in water?

by nonequilibrium
Tags: poisson or arago, spot, water
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Nov7-12, 09:15 PM
P: 1,417

So Poisson's spot is a (peculiar) effect of light due to its wave nature (it's the bright point one would see in the middle of the shadow of a perfectly round coin).

So I was wondering, has Arago's spot been observed for water waves too? For example in a 2D equivalent, i.e. for surface gravity waves.
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Andy Resnick
Nov8-12, 08:42 AM
Sci Advisor
P: 5,523
Interesting.... it seems that there could be, but water waves are slightly different than electromagnetic waves- the dispersion relation for example, and dissipation due to viscosity. Lamb only treats sound waves diffracted though a aperture that is smaller than the wavelength, and those results do not indicate any phenomenon similar to the spot of Arago.

Seems like a good undergraduate project, actually!
Nov8-12, 08:47 AM
P: 11,925
The 2D equivalent would be like an inverted single slit experiment - should be observable.

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