Here's an interesting website:

http://micro.magnet.fsu.edu/primer/j...einteractions/

Destructive and constructive interference can be explored
using a javascript application. What is asserted at the
bottom of the page is particularly interesting:

"In addition, when two waves of equal amplitude and wavelength
that are 180-degrees (half a wavelength) out of phase with each
other meet, they are not actually annihilated, as suggested in
Figure 1. 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 (photons are not capable of self-
annihilation). 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.
Therefore, simple diagrams, such as the one illustrated in Figure 1,
should only be considered as tools that assist with the calculation of
light energy traveling *in a specific direction*." i.e. if Figure 1
didn't ignore reflections, there would be wave(s) traveling off in
some other direction(s).

Translating this to the match point in a transmission line with
reflections: Destructive interference between two reflected waves
cause the elimination of reflections toward the source in a matched
system. "All of the photon energy present in these (canceled) waves
must somehow be recovered or redistributed in a new direction, ..."

There's only one other direction in a transmission line and that's
back toward the load. When the reflected energy is re-reflected
(redistributed) at a match point, it is simply following the existing
laws of EM physics.
--
73, Cecil, W5DXP