Jim Kelley wrote:
So your claim is that energy is delivered by two waves that are equal in
amplitude and opposite in phase?

Naturally, zero energy is delivered in the direction of the complete
wave cancellation. The energy in the two canceled waves is delivered
in the opposite direction from their power-flow vectors. Anything else
would violate the conservation of energy principle.

It's not really my claim. That is what is claimed by the Melles-Groit
and Molecular Expressions web pages. That is what is claimed by Hecht,
in "Optics". That is what is claimed by Walter Maxwell in "Reflections".
Walt calls it a "virtual short". I had forgotten that he had described
it so well until I re-read it. Walt's QST articles in the 70's were where
I encountered these principles for the first time.

Maxwell, Walter, Reflections II, © 2001 Worldradio Books

Page 4-3, "The destructive wave interference between these two complementary
waves ... causes a complete cancellation of energy flow in the direction toward
the generator. Conversely, the constructive wave interference produces an energy
maximum in the direction toward the load, ..."

(I had forgotten about that being in "Reflections". "Optics" was only
a refresher of the "Reflections" material.)

Page 23-9, "Consequently, all corresponding voltage and current phasors are 180
deg out of phase at the matching point. ... With equal magnitudes and opposite
phase at the same point (point A, the matching point), the sum of the two
(reflected) waves is zero."

Waves cannot even exist without energy.

Correction. Waves cannot be created without energy. Electromagnetic
fields can indeed exist without necessarily conveying energy from one
place to another.

Correction. DC electromagnetic fields can exist without conveying energy
but the context is RF EM waves. EM wave-fields cannot exist without energy.
They can only exist at the speed of light, i.e. with ExM joules/sec
passing a point. The use of your tricky-dicky definition for "convey"
doesn't change those facts of physics.
--
73, Cecil http://www.qsl.net/w5dxp


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