Cecil Moore wrote:

Powers obey the equation P1 + P2 + 2*(P1*P2)cos(theta)

I thought you said nature doesn't obey math models. :-)

P1 + P2 would be superposing powers. I didn't do that.

P1 + P2 + 2*sqrt(P1*P2)cos(theta) is NOT superposing powers.

You do understand that interference is the result of the superposition
of waves traveling in the same direction, right?

Eugene Hecht would be surprised to hear you say such since he
talked about the powers (irradiance) of various reflections in
the same media.

Again Cecil, you're really in no position to speak on his behalf. He
might not think that highly of your doing so in fact. Perhaps you
should obtain his permission first.

I did not superpose powers. I used Hecht's equations for powers
(irradiance).

Actually, the fact that those equations appear in his book (as well as
just about any other optics book) does not convey any rights of
ownership or invention to the author. They were around a long time
before Dr. Hecht.

The only difference in irradiance and power is
the unit-area which, for our example, is arbitrary.

You should show him your equation with all the power terms (P1-P4) in
it! You had some of the powers going one way, and the others going the
other way. You needed them all to add up to some particular number, so
you just added them. - or maybe subtracted some of them. I don't recall
exactly.