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Index of refraction

  1. Dec 4, 2005 #1
    I am having a little bit of trouble finding the speed of light in a given medium when you are only supplied with the index of refraction. For example, I was given that n=1.36 in ethanol, and I had to find the speed of sound in ethanol. I know the equation for the index of refraction is n=c/v, but I am having problems with actually using it. For example, when only given that the index in a vacuum is 1.0, how do you know the speed, or do you use 300,000 km/s? Just a little bit confused here.
  2. jcsd
  3. Dec 4, 2005 #2
    the index of refraction = speed of light in vaccuum/speed of light in the medium.

    put in the knowns. solve for the unknowns.
  4. Dec 4, 2005 #3
    you already know the answer.
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