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Originally posted by DragonsDemesne
The following is from my textbook "Optics" 4th edition by Eugene Hecht (which has the added bonus of being something I need to know for my final on Thursday, hehe)
...blah blah... some math derivations... we can arrive at an expression for n as a function of w, which is known as a dispersion equation:
n^2 = 1 + [(Nq^2)/(E*m)]*[1/(wo^2 - w^2)]
(gotta love trying to put formulas into a forum, lol)
n = index of refraction
q = elementary charge = 1.6*10^-19 C
E = permittivity of free space = 8.85*10^-12 F/m
m = mass of an electron
N = number of electrons in the volume being looked at
wo = resonant frequency
w = frequency of EM wave coming in (i.e. the light wave)
So at frequencies above resonance, (when w>wo) then the right hand side of the equation is going to be 1 + (something negative) = something smaller than 1.