K7ITM wrote:
Of course, it does not require coherent sources to see the effects of
interference.

True, but it does require coherent waves to accomplish
the permanent wave cancellation described at:

micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/waveinteractions/index.html

"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the photon energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, so
the effect should be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction or destruction of
light."

This is what happens to the reflected waves at a Z0-match
in a transmission line.
--
73, Cecil http://www.w5dxp.com