Re: [Phys-l] Snell's law, critical angle and Huygen's construction

[brian whatcott <betwys1@sbcglobal.net>]

 I think this is a much better way of describing the active principle.
On exit where the relative index is negative, as it were, the 
reciprocity with
the entrance wavefront's deviation is apparent.

Brian W

On 9/19/2010 11:32 AM, Bernard Cleyet wrote:
> I think the derivation assumes an isosceles cross section and equal entrance and exit deviations.
>
>
> bc too lazy to check
>
>
> p.s. My favo. and the reason out of print (perhaps?), leave it to the student to use optical reversibility to show when the deviation is min. the path of the beam is symmetric, then derive the equation.  the former implies (in an isosceles) parallelity.  No?
>
>
>
> On 2010, Sep 18, , at 20:15, brian whatcott wrote:
>
> >   How far can you trust a source that repeatedly defines the angle of
> > minimum deviation in a prism, in this way?
> >
> > "Prisms are typically characterized by their angle of minimum deviation
> > d. This minimum deviation is achieved by adjusting the incident angle
> > until the ray passes through theprism parallel to the bottom of the prism"
> >
> > Brian W