Jim Kelley wrote:
Not exactly as per Hecht. Note to the casual reader: please be advised
that unlike Cecil, Eugene Hecht does not claim that power is equal to
irradiance.

It's only fair to tell everyone reading your posting that
you do not accept the definition of power in the IEEE Dictionary
nor the definition of power used by the average RF engineer.
Irradiance, Poynting vectors, and power flow vectors are valid
concepts no matter what esoteric definition of power that you
choose to assert.

Hecht gives the dimensions of irradiance which are the same
as the Poynting vector (power flow vector) in RF engineering.
That you don't consider watts to be power is no reason to
question the validity of irradiance or Poynting vectors.
I don't have "Optics" with me at work so I cannot do an
exact Hecht quote.

Nor does he imply that scaler quantities can be treated
mathematically in the same way as vector quantities, and he therefore
does not substitute power for irradiance in any of his textbook
equations as Cecil has want to do.

I am using Hecht's irradiance equations. Whatever Hecht
implied by those equations is exactly what I am doing. Any
angle used in the irradiance equations is the angle between
the electric fields of the two superposed waves.

It was not me, but Dr. Best, who first substituted power for
irradiance in his series of QEX articles. But Poynting vectors
can obviously be substituted for irradiance since they represent
the same thing and have identical dimensions. Most RF engineers
would assert that Poynting vectors and power flow vectors represent
power. It is your narrow definition of "power" that is the culprit
here, not anything I have said.

If it will make you feel better, forget the power equations and
call them the power flow vector equations. I will try to remember
to do that in the future.

These equations do in fact give correct results macroscopically.
However, it is inaccurate to infer from interference equations that a
given electromagnetic wave is 100% reflected from any partially
reflecting boundary. It is only after multiple partial reflections from
the inner boundaries of the intermediate medium that the total energy
from any given wave in conveyed from source to load.

All the values are average *steady-state* values, the same values
that would be read by a Bird directional wattmeter. All multiple
reflections are rolled into the average Iref value displayed by
the Bird. All multiple forward components are rolled into the
average Ifor value displayed by the Bird.
--
73, Cecil, http://www.qsl.net/w5dxp