A certain material has a single absorption band which runs from photon energy E1 to E2. If the absorption coefficient is constant within this band and 0 elsewhere, show that refractive index for E<E1 is $n(E) - 1 \approx \frac{1}{E} \ln \frac{(E_2 - E)(E_1 + E)}{(E_2 + E)(E_1 - E)}$
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The absorption coefficient is constant within the absorption band. This means that the probability of a photon being absorbed by the material is the same for all photon energies within the band. Show more…
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