Relating absorbance wavelengths and refractive index

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SUMMARY

This discussion centers on the relationship between absorbance wavelengths and refractive index values, specifically addressing the feasibility of translating absorbance λ values into refractive index values. The Sellmeier equation, which requires experimentally determined coefficients, is mentioned but deemed unrelated to the primary inquiry. Instead, the Kramers-Kronig relations are highlighted as a method to derive the real component of the refractive index from the imaginary component, represented by absorption values. Understanding the units associated with absorption measurements is crucial for accurate calculations.

PREREQUISITES
  • Understanding of absorbance and its relation to refractive index
  • Familiarity with the Kramers-Kronig relations
  • Knowledge of the Sellmeier equation and its application
  • Basic grasp of Snell's law and its components
NEXT STEPS
  • Research the Kramers-Kronig relations in detail
  • Explore the Sellmeier equation and its coefficients
  • Study the Hilbert transform and its application in optics
  • Investigate the units used in absorption measurements and their implications
USEFUL FOR

Biologists, physicists, and optical engineers interested in the relationship between absorbance and refractive index, as well as those looking to apply Kramers-Kronig relations in their research.

kajendiran56
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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.
 
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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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