Relating absorbance wavelengths and refractive index

  1. Dear All,
    thank you for your attention. I am a Biologist and I was wondering if it is possible to translate absorbance λ values into a refractive index value? I found out about the sellmeier equation however it appears to require coefficients that have to be experimentally determined.

    Is there a way around using these coefficients? I just need to know if it is possible or not and pointed in the right direction.
    Thank you for your time.
  2. jcsd
  3. Andy Resnick

    Andy Resnick 5,785
    Science Advisor

    Absorption can be treated as an imaginary component of the refractive index, n = n' + in'', where n' is the real component and is used in, for example, Snell's law. If you have n''(λ), the absorption, you can calculate the real component via Kramers-Kronig relations (the real part is the Hilbert transform of the imaginary part and vice-versa), but the details will depend on the units associated with your absorption measurement.

    The Sellmeier equation is an empirical dispersion relation for the real part of the refractive index, and is unrelated to your question.
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