W5DXP wrote:

Jim Kelley wrote:

W5DXP wrote:
I don't think there's anything to argue about. From _Optics_, by Hecht:
"We define the reflectance R to be the ratio of the reflected power to
the incident power."

He certainly wasn't including Max Born and Emil Wolf when he said "We".
They define reflectance in terms of indices of refraction i.e.
(n1-n2)/(n1+n2).

The Reflectance is equal to the square of the amplitude reflection
coefficient.
R = Ir/Ii = [(n1-n2)/(n1+n2)]^2

Again, Born and Wolf disagree with Hecht. They define Reflectivity as
being the square of the reflection coefficient.

Hecht says the definition "leads to" the last term above.

Certainly he didn't feel that some relative amounts of power are what
determine the indices of refraction of the system. That would be
ridiculous.

73, ac6xg