Re: glass ...

[Jim Pengra <pengra@whitman.edu>]

> > One measures the angle A of the prism, and delta the angle of minimal
> > deviation for a selected wavelength, and then the refractive index
> > relative to air ( mu) is given by
> >
> >  mu = sin 1/2 (A + delta)/sin 1/2 A
>
> The trouble with this method is that the minimum is practically flat over
> the broad range of angles. Thus a very large uncertainty will always be
> associated with delta. I nice mathematical relation, but not very useful
> for measuring mu.

   But it's not delta that's imprecise, it's the position of minimum
deviation. This means that you don't have to sit exactly on the position of
minimum deviation to get a good value for delta and hence a good value for
mu. The precision of delta (and A) depends only on your skill and the
quality of the angle  measuring apparatus.


--Jim(pengra@whitman.edu) Walla Walla, Washinton 99362