Re: Antonym of 'evanescent'?


"Salmon Egg" <SalmonEgg@xxxxxxxxxxxxx> schrieb im Newsbeitrag
news:C38DB8EA.13476%SalmonEgg@xxxxxxxxxxxxxxxx
On 12/18/07 9:18 AM, in article
siegman-9752FD.09181318122007@xxxxxxxxxxxxxxxxx, "AES"
<siegman@xxxxxxxxxxxx> wrote:

What is -- or should be -- the antonym of 'evanescent' *in optics*?

["Temporary" and "permanent" just don't do it.]

I am a great fan of using the equivalent wave impedance or admittance of a
wave. In appropriate units, admittance is the index of refraction. See
"Fields and Waves in Modern Radio," by Ramo and Whinery and its
successors.
Evanescent corresponds to a pure imaginary characteristic impedance, or
characteristic index. That allows for fields with zero power factor in the
direction of propagation.

Realize that there can be propagation in an evanescent wave. For example,
in
total internal reflection there is propagation parallel to the boundary
and
none perpendicular to it.


No. The resulting energy flux has only a component parallel to the surface.
But in order to come behind the surface there is necessary a hop into the
wave behind and a hop back.

As a rambling thought, maybe a more meaningful tensor quantity can be
devised to replace the Poynting vector. As a cross product, the Poynting
vector already is a pseudovector. Maybe equivalent wave index can be
thought
of as a tensor.


No. There exists a second flux density (spin flux density) for spins
which has no classical counterpart. The spin density (spinergy)
can have negative values (energy density only positive !)

Bill



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