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Speed of light again

  1. Nov 14, 2005 #1


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    The path of light in a known medium in a gravity well is x, is the path of the light still x in
    a dencer medium ?
    Last edited: Nov 14, 2005
  2. jcsd
  3. Nov 14, 2005 #2


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    Since light's path can be bent when it travels through a medium in ordinary flat spacetime (see here and here), the answer must be "no". But it would depend on the index of refraction, not the density.
  4. Nov 14, 2005 #3
    Doesn't the deviation of the light's path also depend on the local variation of the medium's density ? Just like in the case of dispersion (ie "white" light splits up into different frequencies when it passes through a medium)?

    Or what about absorption of photons by the medium's atoms and the subsequent emission into "other" directions than the incident direction.

    My point is, shouldn't we tackle this question from a QM point of view ?


    ps : i do realize that mentioning QM in this subthread is a bit, err, contradictory, but anyhow, what are your thoughts on this ?
    Last edited: Nov 14, 2005
  5. Nov 14, 2005 #4


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    Well, when I said it would depend on the index of refraction rather than the density, I didn't mean to rule out the idea that the density of the medium could itself influence the index of refraction, it's just that other things would presumably influence it too. I don't know enough to say what physical properties of a medium determine the refraction index, I think you're right that you'd need to get into QM to understand it.
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