Re: was REFLECTION AND REFRACTION

[phrp@bigcat.fhsu.edu (Roger Pruitt)]

LUDWIK KOWALSKI wrote:
> Does the Fermat Principle explain refraction? It does for me. Why?
> For the same reason for which the energy conservation law makes me
> understand why a tennis ball released from a rest position never
> bounces to a higher elevation. (For those who are more pedantic I
> may add that "the internal properties of a tennis ball do not
> change in the process".) I have a model of explanation and my
> understanding can be defined as a process of matching observations
> to that model. My understanding may not be valuable to her or him
> but that is their problem, not mine. Unless I am their teacher,
> of course.
>                                                  

Aren't there various levels of explanation? Fermat's Principle and
Snell's law explain at one level. At a deeper level there is the
understanding based on propagation of electromagnetic waves which gives
details. After seeing and working through refraction based on the
latter, don't we generally revert to working with Snell's law or
Fermat's Principle since the propagation details will end up generally
giving us Snell's law?

It seems to me that the principle of conservation of energy, necessary
and powerful as it is, doesn't really explain why a tennis ball,
released from a rest postion, never bounces to a higher level. The
details of the process are left out. 

Roger Pruitt