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Bubbles on top of water

  1. Sep 10, 2014 #1
    Recently I went to a pool, and observed that when we hit the water/ create waves on the top layer of it, bubbles emerge.

    It may sound like a silly question, but it really got stuck in my mind..Why does this happen?

    Thank you for your answers in advance.

    P.S: I am new to this forum, I hope that I opened this thread in the right section.
  2. jcsd
  3. Sep 10, 2014 #2
    Normally bubbles won't form on the surface unless there's some sort of surfactant (soap) involved.
  4. Sep 10, 2014 #3
  5. Sep 10, 2014 #4

    Andy Resnick

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    Education Advisor

    Are you referring to foam?
  6. Sep 10, 2014 #5


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    Staff: Mentor

    You chose the right forum, and there's nothing silly about this sort of question - the physics of a good-sized object (chances are that you weigh many tens of kilograms) hitting water are complicated and interesting. Google might find you some high-speed images and videos of what's going on.

    Several things to consider: First, as you are about to hit the water, the air between you and the surface will not be able to escape before you reach the surface - that air will be driven under water and will have to make it back to the surface as bubbles. Second, as you push below the surface, both air and water will rush in to fill the space above you, and some of the air may end up underneath the water - another source of bubbles. And as KL7AJ points out, any surfactant (or even surface contaminant) in the water will affect how long the bubbles last and how noticeable they are.
  7. Sep 10, 2014 #6
    Don't forget that some air is also trapped inside your bathing suit, and has to escape.

  8. Sep 11, 2014 #7
    Thank you for your answers, there was no surfactant in the water, so I understood what happened, reading Nugatory's explanation.
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