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Dark places.

  1. Feb 16, 2008 #1
    Rough (not smooth) surfaces often appear to be darker in sunlight when they are covered by water.How can we explain this physical phenomen?
  2. jcsd
  3. Feb 17, 2008 #2


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    I'm no expert in this by any means, but I suspect that it's due to polarization of the light coming back from the water.
  4. Feb 17, 2008 #3
    Can it be total internal reflection.In this case light cannot go out from the liquid.
  5. Feb 17, 2008 #4


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    Not total, or you would see nothing at all. Honestly, though, wait for someone with appropriate knowledge to help you. I'm not qualified. I just guessed at the polarization because a very long time ago when I wore Polaroid sunglasses, a puddle on a sidewalk looked to be a couple of miles deep. Without the glasses, it was just a puddle.
  6. Feb 17, 2008 #5


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    First off you will have some of the light reflected off the surface so not all the light makes if through the water to the object.
    Then some of the light is also reflected back into the water when it encounters the boundary again on its way out.
    You will also have some of the light absorbed by the denser medium.

    At least the would be my guess.

    This would be true for both smooth and rough objects though.
    Maybe it has to do with the angle of incidence and the angle of refraction.
    Last edited: Feb 17, 2008
  7. Feb 17, 2008 #6
    The effect has more to do with the fact that by coating the object with water, a good deal of light is reflected off the surface, instead of being scattered in random directions by the rough, dry surface.
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