Richard Harrison wrote:

Cecil, W5DXP wrote:
"Seems to me, canceled waves must "cease to exist" at a point in space
time if they exhibit zero measurable evidence of their existence forever
after---."

A union of two waves can make them both disappear if they are exact
opposites, but elimination of just one of the two produces the the
other. Were the two waves actually annhilated by their coexistence on
the path together, they would not be exhibitable on demand by
turning-off one or the other constituent.

Of course they would, Richard, since the destructive interference ceases
when one of them is turned off. What happens while the two waves are
engaging in total destructive interference is that their combined energy
components flow in the opposite direction as a constructive interference
wave. That's why Melles-Griot says the rearward flowing "lost" energy
involved in the destructive interference is not lost at all and instead
joins the forward wave traveling in the opposite direction. That's why
the rearward-flowing reflected wave energy all winds up flowing toward
the load in a Z0-matched system.

Let's say I am a light year away from two interfering waves at your
location. I am measuring zero energy. You switch off one of the signals.
How long does it take for me to sense any energy? - a year because the
energy pipeline is empty before you switch off one of the signals.
There's no energy flowing toward me while both signals are on.
--
73, Cecil http://www.qsl.net/w5dxp



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