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About bose-einstein condensate

  1. Aug 31, 2004 #1
    how does light slow down considerably when it passes through one? i have always been told that lights speed remains constant. as with many questions, i have my own personaol theories for answers, but i want to find out for sure.
  2. jcsd
  3. Aug 31, 2004 #2


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    The speed of light through a vacuum is constant; the speed at which light propogates through various substances can differ significantly. Now you must realise, the actual speed of the light is still constant, but the light passing through a medium will get absorbed by atoms within that medium (where the energy from the light "pauses" for a moment, not moving at all), then re-emitted. The amount of time the light energy is trapped in the atom determines the speed at which light appears to be moving through that medium, but this is actually the result of light coming to a dead stop, then moving on at c, over and over again.

    This is not a property exclusive to BEC's, most if not all mediums slow the progress of light.
  4. Aug 31, 2004 #3
    i see. i knew that light speed only remained constant in a vacuum, but i suppose my true question was why it didn't remain so in a medium
  5. Sep 1, 2004 #4


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    Then you need to understand (i) the difference between group velocity and phase velocity; (ii) the mechanism of optical conductivity in gasses and non-vacuum media (I have written lengthy essays on this somewhere in here) and (iii) how we actually detect what is moving at what speed in anything.

  6. Sep 2, 2004 #5


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    Zz, does this not get boring at times? It does for me. I get really tired of trying to explain the same thing over and over and over. If I had a theory-busting concept I would at least show the math. Pardon my disrespect for the math challenged.
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