In 1871 Sellmeier derived the equationwhere the Aj terms are constants and each λoj is the...

In 1871 Sellmeier derived the equation

where the Aj terms are constants and each λoj is the vacuum wave- • length associated with a natural frequence voj, such that λojvoj = c. This formulation is a considerable practical improvement over the Cauchy Equation. Show that where λ >> λoj, Cauchy's Equation is an approximation of Sellmeier's. Hint: Write the above expression with only the first term in the sum; expand it by the binomial theorem; lake the square root of n2 and expand again.