Jim Kelley wrote:
What has been known since long before you were born is that only direct
interaction with matter causes EM waves to reflect. You're far too
modest Cecil. The "4th mechanism of reflection" is completely your
idea! ;-)

Nope, it's not. The interference is caused
by the interaction of the forward and reflected waves
*at a physical impedance discontinuity*. The impedance
discontinuity is the primary cause of everything and is
certainly a point of "direct interaction with matter".
The reflection coefficients based on RF impedance
discontinuities are similar in kind to the reflection
coefficients based on differing light indices of
refraction between materials.

The forward reflection of light from a non-reflective
thin-film glass surface was well understood before I was
born. Optical engineers have no problem with that change
of EM wave momentum due to interference between the internal
reflection and the external reflection. That's the same
mechanism that happens at a Z0-match point in a transmission
line.
--
73, Cecil http://www.w5dxp.com