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Poisson/Arago's spot in water?

  1. Nov 7, 2012 #1

    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.
  2. jcsd
  3. Nov 8, 2012 #2

    Andy Resnick

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    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!
  4. Nov 8, 2012 #3


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    The 2D equivalent would be like an inverted single slit experiment - should be observable.
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