Thread: Brainteaser
View Single Post
  #41   Report Post  
Old May 31st 06, 12:14 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
Posts: n/a
Default Brainteaser

"Jim Kelley" wrote in message
...

Cecil Moore wrote:
Yes, but the 200 joules in the line was previously sourced
by the generator during the transient state. It's hard to
sweep 200 joules under the reflected power rug.


So is this your proof that Joules of energy are likewise reflected from
antireflective surfaces?


No, the two subjects are conceptually only distantly related so your
posting is a diverting of the above issue - changing the subject back
to an earlier thread:

Every impedance discontinuity causes reflections. An antireflective
surface is an impedance discontinuity, i.e. a change in the index of
refraction between two mediums. If properly designed, the anti-reflective
surface causes 100% destructive interference between the internal and
external reflections each of which contain joules of energy. It is easy to
prove
that the internal reflection contains joules of energy. If the external
reflection
didn't contain any energy, then destructive interference would not be
possible. Therefore, both reflections associated with an antireflective
surface must contain an equal magnitude of joules.

In his QEX article, Dr. Best gave us the physics equation that governs
100% destructive interference: Ptotal = P1 + P2 - SQRT(P1*P2).
Assuming that power cannot exist without energy, if the energy in P1
equals the energy in P2 and the associated waves are 180 degrees out
of phase, then of course 100% destructive interference occurs at the
antireflective surface. That's how antireflective surfaces and Z0-matches
work.
--
73, Cecil http://www.qsl.net/w5dxp