Jim Kelley wrote:
You want people to believe that the behavior of an antireflective
coating is, first light reflects from it, and then it's cancelled -
before anybody see's it. That's trying to have it both ways.

No, that is obviously what happens, Jim. Since it happens
at the speed of light, our eyes just cannot see it. But
for the instant of time it takes the light wave to travel
the 1/2WL round trip through the thin-film and back, there
exists a reflection from the thin-film. The laws of physics
will not allow anything else.

It's a lot easier to detect at RF frequencies where 1/4WL
takes some time for the RF wave to travel. For instance,
1/4WL at 4 MHz is 61.5 feet. It takes RF a measurable
length of time to travel that distance and for that length
of time during the transient state, a reflection exists
which is canceled if a Z0-match is achieved. That's just
simple physics. Here is an example:

XMTR---50 ohm T-line---+---1/4WL 291.4 ohm T-line---50 ohm load

Rho at the impedance discontinuity is 0.707. For the length
of time it takes the first reflection to arrive back from
the load at point '+', 1/2 of the forward power is reflected
back toward the source. That's a reflected wave that is
subsequently canceled. Exactly what causes the cancellation
of that reflected wave? You have *never* answered that
question.
--
73, Cecil http://www.w5dxp.com