Poisson/Arago's spot in water?

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SUMMARY

Poisson's spot, a phenomenon observed in light due to its wave nature, raises questions about its occurrence in water waves, specifically surface gravity waves. The discussion highlights that while Poisson's spot is well-documented for electromagnetic waves, similar effects in water waves are complicated by differences in dispersion relations and viscosity. Notably, Lamb's work on sound waves does not provide evidence for an analogous effect in water. The conversation suggests that investigating Arago's spot in a 2D water wave context could serve as a valuable undergraduate research project.

PREREQUISITES
  • Understanding of wave phenomena, specifically Poisson's spot
  • Familiarity with surface gravity waves and their properties
  • Knowledge of dispersion relations in different wave types
  • Basic principles of viscosity and its effects on wave behavior
NEXT STEPS
  • Research the properties of surface gravity waves in fluid dynamics
  • Explore the mathematical formulation of dispersion relations for various wave types
  • Investigate experimental setups for observing wave diffraction, such as the inverted single slit experiment
  • Study the effects of viscosity on wave propagation and diffraction
USEFUL FOR

Students and researchers in physics, particularly those interested in wave mechanics, fluid dynamics, and experimental physics. This discussion is particularly beneficial for undergraduate students seeking project ideas related to wave phenomena.

nonequilibrium
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Hello,

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

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