Jim Kelley wrote:
You seem to be implying that there's something different about how these
electromagnetic waves change direction compared to other electromagnetic
waves. Why is that?

There is something different but not unusual. We don't
often observe wave cancellation of visible light waves
because of the problem of getting coherent beams of light
perfectly aligned. Yet, we experience RF wave cancellation
every time we adjust our antenna tuners for a Z0-match
because the perfect alignment of coherent RF waves inside
a piece of coax is an automatic given.

Here's a very simple example. The measured forward
and reflected powers are given. The source and load
impedances are irrelevant and the length of the Z01
and Z02 lines are irrelevant. Any one of these
measured values could be unknown and solved for by
calculations based on the conservation of energy
principle.

------Z01------+------Z02------
Pfor1=100w-- Pfor2=200w--
--Pref1=0w --Pref2=100w

We have 100 joules/sec incident upon the Z0-match
point from the direction of the source. We have 100
joules/sec incident upon the Z0-match point from
the direction of the load. Those waves combine
to obtain 200 joules/sec toward the load. It is
obvious that Pref2 has to change direction and
momentum for that condition to exist.

The power reflection coefficient, rho^2, is obviously
0.5 so the voltage reflection coefficient, rho, is
just as obviously +/- 0.707, depending upon whether
[Z02 Z01] or [Z02 Z01}.

The direction and momentum of the Pref2 reflected wave
obviously reverses at the Z0-match point '+'. Exactly
how does the direction and momentum of the Pref2 wave
get reversed? Where are the physics equations for that
process that we hams label "re-reflection"? You and others
have been strangely silent on that subject preferring to
kibitz rather than provide any technical insight.

An exact duplicate of the above conditions would exist
with a 100w laser beam traveling through 1/2WL of thin
film with an index of refraction of 5.83.

A B
i=1.0 | i=5.83 | i=1.0
100w laser---air---|--1/2WL thin-film--|---air---...
--Pref1=0w | --Pref2=100w | --Pref3=0w
Pfor1=100w | Pfor2=200w-- | Pfor3=100w--

What happens to reverse the direction and momentum of
the internal reflection in the thin film? Hint: Both
Hecht and Born & Wolf give the equations for what happens
at plane A. And yes, the S-Parameter equations agree 100%
with them.
--
73, Cecil http://www.w5dxp.com