On May 30, 9:04*pm, Richard Clark wrote:
There is nothing about sinusoidal waves that make
them coherent or colinear.

Please Google the two words: I probably should have use "collimated"
instead of "collinear".

"Electromagnetic radiation is coherent when the photons are produced
in such a way that they are in phase with one another and incoherent
when the phases of the photons are random."

"Collimated light is light whose rays are nearly parallel, and
therefore will spread slowly as it propagates. The word is related to
"colinear" and implies light that does not disperse with distance
(ideally), or that will disperse minimally (in reality)." Note that a
coaxial transmission line results in minimal dispersion for an RF
wave.

Coherent photons are identical except for direction. Collimation makes
their direction close to identical.

Permanent - another superstition (until the end of time + 1 day?).

Wrong definition of "permanent". Not permanent in time - permanent in
the sense that the process is irreversible in time.

As I undestand, two o more superposed waves can be added or
substracted to render a resultant but we do not call that interaction

We do call it interaction when the two waves are coherent and
collimated. Again, here is what Florida State University has to say:

"... when two waves of equal amplitude and wavelength that are 180-
degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the photon energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, so
the effect should be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction or destruction
of light."

They are talking about wave cancellation such that happens at the
surface of the thin-film on non-reflective glass. The result of wave
cancellation is permanent and the energy that would have been
reflected is reversed in direction actually making the underlying
picture brighter. That sounds permanent to me.

They interact on the load, not on each other.

If that were a fact, you could separate them on their way to the load
but such is impossible. It doesn't matter where they came from, two
coherent, collimated waves interact when they are superposed and
become inseparable from that point on. Only incoherent or uncollimated
photonic waves can be separated.

And if you allow interaction at the load, why not allow interaction at
an impedance discontinuity which is much like a load and is indeed
where the interaction happens.

This says nothing of waves interacting, however. *That is sheer
nonsense.

Wave cancellation is an obvious proof of interaction. Let's see you
recover two waves that have been canceled.

Let's put it another way and agree entirely! *Accept that two coherent
waves that are colinear do interact - but only if colinear. *That must
be some very, very special mathematics that allows no error in
colinearity (perfection is demanded). *Perfection does not exist, the
necessary colinearity does not exist, interaction does not exist.

"Perfection does not exist" is the self-fullfilling last gasp non-
perfect argument of the ignorant. Close enough to collimation
perfection does exist in an RF transmission line or in an
interferometer. The coherent photons in an ideal coaxial transmission
line are forced into a state of collimation. Is it perfect single-file
collimation? Of course not, but it doesn't have to be perfect.
Confining the photons to a certain cross-sectional area is all that is
required in the real world. Do all the photons have to be perfectly
coherent? No, just the majority of photons from the transmitter.

Does a 1/4WL non-reflective coating on glass perfectly cancel 100$ of
the single-frequency coherent incident laser light? Not in the real
world, but you can use your own eyes to detect that it is doing a
pretty good job. The Melles-Groit web page says:

"In the absence of absorption or scatter, the principle of
conservation of energy indicates all 'lost' reflected intensity will
appear as enhanced intensity in the (forward) transmitted beam. The
sum of the reflected and transmitted beam intensities is always equal
to the incident intensity. This important fact has been confirmed
experimentally."

Those above alluded-to experiments seem to contradict what you are
asserting. Do your own experiments disprove what that web page is
saying? If so, where did they go wrong?
--
73, Cecil, w5dxp.com