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Calculating refractive index

  1. Mar 24, 2012 #1
    How can i calculate the refractive index knowing only the frequency of the light entering the medium from air?

    n(refractive index) = (speed of light in vacuum) / (speed of light in medium)
  2. jcsd
  3. Mar 25, 2012 #2


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    You can't, unless you are provided with a formula for the refractive index in terms of frequency or wavelength.

    p.s. Welcome to Physics Forums.
    Last edited: Mar 25, 2012
  4. Mar 25, 2012 #3
    Yeah, I think the problem I have here doesn't have all the information. Thanks anyway! Thanks also for welcoming me here ^^
  5. Mar 25, 2012 #4
    I believe that for real indexes of refraction, Re (n(λ)) = c/v(λ).

    If the index of refraction varies with wavelength (dispersion), then there is absorption as well as dispersion, which is equivalent to a complex index of refraction. See http://en.wikipedia.org/wiki/Refractive_index
    See in particular the section on Complex index of refraction and absorption.
  6. Mar 25, 2012 #5


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    But in this situation we don't have v(λ), we only have the frequency [itex]\nu[/itex]. From that we can get λ in air, but not λ in the medium or v(λ) for that matter.
  7. Mar 25, 2012 #6
    I should have said for ANY n(λ), the velocity v(λ) = c/Re (n(λ))
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