Richard Clark wrote:

Cecil Moore wrote:
I guess you will take that delusion to your grave.

Yet more guessing?

It's a guess as to whether you are going to correct
your errors about thin-film coatings before you
expire. What is it about the following that you don't
understand?

www.mellesgriot.com/products/optics/oc_2_1.htm

"Thin-Film Interference"

"Thin-film coatings also rely on the principles of interference. Thin
films are dielectric or metallic materials whose thickness is comparable
to, or less than, the wavelength of light."

Speaking of 1/4WL thin-film coatings:

"Clearly, if the wavelength of the incident light and the thickness
of the film are such that a phase difference exists between reflections
of p, then reflected wavefronts interfere destructively, and overall
reflected intensity is a minimum. If the two reflections are of equal
amplitude, then this amplitude (and hence intensity) minimum will be
zero."

"Amplitude minimum equal zero" means all reflections have been eliminated.
--
73, Cecil http://www.qsl.net/w5dxp