In 1871 Sellmeier derived the equation

where the A_j terms are constants and each λ_0j is the vacuum wavelength associated with a natural frequency v_0j, such that λ_0jv_0j = c. This formulation is a considerable practical improvement over the Cauchy Equation. Show that where λ > > λ_0j, Cauchy€™s Equation is an approximation of Sellmeier€™s. Write the above expression with only the first term in the sum; expand it by the binomial theorem; take the square root of n² and expand again.

Transcribed Image Text:

Ад? r = 1+ ):