Re: Goethe Contra Newton: the Prism Experiment


"Gernot Hoffmann" <hoffmann@xxxxxxxxxxxx> wrote in message
news:1121271142.453042.264460@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Sellmeier's Equation
>
> http://en.wikipedia.org/wiki/Sellmeier_equation
>
> describes the refraction coefficient n (refractive index)
> e.g. for glass as a function of the wavelength: n = n(La).
>
> The formula and the plot are matching.
> If this formula should have been based on fitting measured
> data, then it's IMO a quite unusual mathematical model.
>
> 1. Is the formula correct (concerning exponent +2 for C3) ?
>
> 2. Does anybody know a power series substitute for the
> range of visible light ? Here in micrometers:
> La = 0.360 to 0.800, e.g. for Lr = 0.550 as reference .
> n = a0 + a1*(La-Lr) + a2*(La-Lr)^2 + a3*(La-Lr)^3 ...
>
> Best regards --Gernot Hoffmann
>

The link that you give does not show an equation of the form of a 3rd
polynomial in Delta Lambda. The formula shown in the en.wikipedia.org link
is identical to the equation given by Schott - a leading supplier of optical
glass in Germany. I believe that there is a European website at
www.schott.com. The link states that this equation is empirical.

I have seen references to a polynomial version of the Sellmeier equations
but they are generally higher order than 3. If there is a reference
wavelength it would be a strong emission line - such as the Sodium D line at
589nm (0.589 micron).


.

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