RadioBanter - View Single Post - The Extreme Failure of Poor Concepts in Discussing Thin Layer Reflections

July 26th 05, 08:00 PM

On 26 Jul 2005 13:08:53 -0500, wrote:

You are correct that in this system (1/4-wave matching layer), the
total reflectance goes to zero.

However, your understanding of superposition is wrong. You
CANNOT superimpose POWERS, or even talk about the "power" of various
reflections in the same media. You can only add the wave amplitudes
(electric fields). THEN you take the total amplitude and square that
to get the power.

Hi Tor,

This is all taken care of in the equation for energy conservation that
I posted. The solution is valid barring a simple error of subtraction
that should read:
110mW - 98mW
or
12mW
in that same 1mm², which if we cast to the same terms of comparison to
sunlight it becomes 18000W/M² which is 18 TIMES THE POWER OF THE SUN's
total BW emission. As you may guess I am going to use the same BW
correction to find that the un-cancelled reflection products have
1200 TIMES MORE POWER THAN THE SUN!

All should note that if you have only 98mW (expressed in the correct
terms of course as the area terms have been abandoned) available to
offset 110mW (again with the same proviso) then it stands that Total
Cancellation is always impossible. As the two energy levels are not
equal, there is no other answer.

This is not to confuse the solution with the practical reduction. On
the other hand, when the remaining reflection products contains so
much more power than the sun's exposure, it is doubly amusing to see
it expressed as "0."

73's
Richard Clark, KB7QHC