Keith Dysart wrote:
To be convincing, the various functions of time need to
align appropriately.

And one can tell that they indeed do "align appropriately"
just by looking at the graphs of the two voltages. We know
that the average power in the reflected wave is dissipated
in the source resistor. All that is left to understand is
how long the destructive interference energy is stored in
the transmission line before being dissipated in the source
resistor as constructive interference.

Graphing in ASCII is pretty difficult. Let's see if we
can do it with words. Take a piece of transparent film
and draw the forward voltage to scale. Take another piece
of transparent film and draw the reflected voltage to
scale. Now we have graphs of two voltages that can be
varied by phase. In ASCII, the best I can do is:

------ ----
/ \ /
/ \ forward voltage /
/________________\____________________/_________
\ /
\ /
\ /
------

----------
/ \ reflected voltage
__________/________________\_____________________
/ \ /
/ \ /
----- ----------

For the first 90 degrees of the above graph, the forward voltage
is positive and the reflected voltage is negative. That is
destructive interference so there's an excess of energy that
is stored in the transmission line. For the second 90 degrees,
the forward voltage is positive and the reflected voltage is
positive. That is constructive interference so the excess energy
from the first 90 degrees is sucked back out of the transmission
line and dissipated in the source resistor. Given that the average
reflected energy is dissipated in the source resistor and assuming
we honor the conservation of energy principle, nothing else is
possible.
--
73, Cecil http://www.w5dxp.com