Jim Kelley wrote:
So I'm happy to
leave it to you to explain to Cecil how waves cancel but without
anhiliating the energy "in" them.

No need for that, Jim. Florida State University has done
an excellent job of explaining how wave cancellation
"redistributes" the pre-existing wave energy in "new
directions" such as the opposite direction in a
transmission line (the only other direction possible).

"... 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."
--
73, Cecil http://www.w5dxp.com