Keith Dysart wrote:
So, while the average powers seem to sum nicely to support the
claim, when the actual power as a function of time is examined
it can be seen that the power in the source resistor is NOT the
sum of its dissipation pre-reflection plus the power from the
reflection.

Here's a quote from "Optics", by Hecht, concerning power
density (irradiance). "Furthermore, since the power
arriving cannot be measured instantaneously, the detector
must integrate the energy flux over some finite time, 'T'.
If the quantity to be measured is the net energy per unit
area received, it depends on 'T' and is therefore of limited
utility. If however, the 'T' is now divided out, a highly
practical quantity results, one that corresponds to the
average energy per unit area per unit time, namely 'I'."
'I' is the irradiance (*AVERAGE* power density).

i.e. The irradiance/interference equation does not work
for instantaneous powers which are "of limited utility".
--
73, Cecil http://www.w5dxp.com