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What am I seeing?

  1. Oct 11, 2006 #1
    I got the kids' swimming pool set up again (12 foot diameter x 3 foot
    high straight fiber-sheet sidewall), and again, with the sun high in
    the sky, when I struck the side of the pool I could watch a shimmering
    geometric network procede from the perimeter of the pool in to the
    center where the network gets tighter and fainter and finally
    disappears from view.

    What am I seeing? That is, it is the disappation of the initial
    perturbation, the traveling pressure wavefronts, but what is going on
    so that I can end up seeing "lines of light" that form the network?

    Is this purely

    1. a mechanical effect where the molecules of water are compressed
    together throughout the depth of the liquid into different "cells or
    sacless mebranes", and the more compressed molecules along the edges
    reflect light more (or less) -- forming the appearance of the network?

    2. or is the reflection of more light coming from changes in
    orientation or spins at the molecular level?

    Also, is what I'm seeing in the shimmering network of light one view of
    the trail of the disappating sound wave traveling at the speed of sound
    in water?

    Any thoughts?

    -- Curious in Brookston Indiana.
  2. jcsd
  3. Oct 11, 2006 #2


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    'I\'d want to understand more about what you mean by network.\r\n\r\nIt does sound like you\'re seeing minute surface perturbations that are refracting light. They\'re basically waves but they act like a prism, concentrating light on the bottom along the ridge of the wave.'
  4. Oct 11, 2006 #3


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    Gold Member

    'I\'d want to undertstand better what you mean by network of light.\r\n\r\nMy suspicion is that what you\'re seeing is refraction from miniscule waves on the surface. The waves might be too small to see but they would act as a magnifying glass along their length.\r\n\r\n PF061010waverefraction.jpg \r\n\r\nAs for the convergence, this sounds like what happens in a circular pool. Vibrations in the pool wall are transmitted along the enitre perimeter of the wall and produce a wave in the water at all points around the perimeter. This wave is directed perpendicular to the wall, and rushes toward the dead centre of the pool. \r\n\r\nHowever, it shouldn\'t disappear as it reaches the centre, it should get more pronounced - often ending in a little sploosh shooting up dead centre.'
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