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Soap Bubbles!

  1. Oct 10, 2004 #1
    Hi,
    Why do some soap bubbles stay intact for longer periods?And what is the reason for the changes in color of the bubbles?
    Thanks!
     
  2. jcsd
  3. Oct 10, 2004 #2

    Clausius2

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    I'm not able to answer the second part. As far as I know the existence of soap bubbles is enhanced by means of the surface tension. Although internal pressure is larger than the external one, the proper surface tension is the responsible of the structural stability of the bubble.
     
  4. Oct 10, 2004 #3
    With respect to the colors, if the thickness of the soap film that forms the skin of the bubble is comparable to the wavelength of visible light you get interference effects. A ray of light striking the the film is split into two rays - one is reflected back, the other is refracted into the film. Some of the intensity of the ray refracted into the film is totally internally reflected, but some is transmitted back out of the film. However, it has suffered an optical path change. The intereference of the two rays, the refracted ray and the reflected ray create the colored fringes.
     
  5. Oct 10, 2004 #4

    rcgldr

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    Colors change because the thickness of the soap bubble changes.

    Different fluids have different surface tension qualities, which is why some soap bubbles last longer than others. If it's just soap, then there's probably a best ratio of water to soap and thickness that allows for the longest duration. The issue is gravity and gusts of winds cause the bubble to get too thin to hold the tension and it bursts.
     
    Last edited: Oct 10, 2004
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