Finding refractive index by interpolation

The problem is described here: [Broken]

In question 1 I need to find the refractive indices for both polarizations at 760nm. I'm not quite sure how to go about this - which model of dispersion best fits Calomel?

(I'm done with the exercise itself, now I just need to plug in the refractive indices values to get a numerical result...)

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Interpolation is the process of estimating a value from a discrete set of ordered pairs of data. You could use a linear interpolation, or since you have three rather widely spaced points you could use a second degree polynomial (parabola) to fit the data and extract the interpolated data point. Most graphing calculators have a built in fitting program for this, probably called a quadratic regression. Or you could derive the equation from the three data points you are given and use it to find the additional popint you need.
You could also use other models with fewer coefficients -- since yeah, you only have three points and probably don't want to trucate the Sellmeier series approach by too much (sorry I didn't notice that :uhh:): [Broken]

The Cauchy model is common.
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Thanks, that seems sensible. I'll report back if anything goes awry...

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