Richard Harrison wrote:

Cecil, W5DXP wrote:
"That`s where you are wrong."

This argument has evoked plain statements, i.e., "When waves cease to
exist, they are forced to give up their intrinsic energy." And, "Waves
don`t cease to exist."

The statements need qualifications. Perhaps waves "cancel" without
ceasing to exist.

In the case we've been discussing the waves in fact never exist, except
on paper. This is because, for example, V3 and V4 cancel at the very
point at which they would begin to propagate. Cancellation precludes
their existance because they cancel for any time element (after the
transient period) and for every spacial element one can enter into the
equation. Contrary to what has been suggested, they do not first appear
and then subsequently disappear. Waves cannot just "cease to exist" for
the very same reason that energy cannot cease to exist.

It may be somewhat easier to see this when we consider that each
boundary can be viewed as a radiator, or re-radiator. When a wave
impinges upon it, the boundary conditions and the nature of the incident
wave determine how waves will be re-radiated from it. With a wave
impinging upon the boundary from one direction only, we would have one
outcome. With two or more waves impinging upon the boundary, we may
have a different outcome.

73, Jim AC6XG