Cecil Moore wrote:


It is impossible for a "partially reflective surface"
to reflect 100% of the intensity.

But that's wrong. If it was right, then a partially reflective
surface couldn't be used to prevent reflections either.

Think about the transient period. You're right that after the first
bounce only half the intensity, for example, is apparent. But using
the physical reflection coefficient you can plot the intensity
increase steadily as a function of time all the way up to steady
state. That's because at every time t, the remainder of all previous
reflections are superposed. Yes, interference describes
macroscopically what happens - it's a short cut to steady state. But
nothing about the reflective surface changes - before or after steady
state. It is only your idea of 'energy in the wave' that needs to
change a little.

73, ac6xg