Superposition
 

Cecil Moore wrote:


Hecht says interference
"corresponds" to the "interaction" of two or more
coherent EM waves "yielding a result ...".

I know from corresponding with you for many years that what someone
says, and what you understand them to say are not necessarily the same
thing. In instances such as this you apparently take whatever meaning
you wish from the words. Interference is not the particular kind of
"process" that you have in mind. There are many meanings to the words
'interaction' and 'process'. In the case of wave interference , the
words do mean that waves are 'doing things' to other waves.

73, ac6xg

Superposition
 

Cecil Moore wrote:


The constructive interference in free space occurs before
the antennas, not after them. Such is the nature of
constructive interference which very few posters fully
understand. My original posting was designed to expose
the beauty of constructive interference.


Cecil,

That's the best line of the month. Can you help out with the Hollywood
writer's strike? Leno and Letterman need some help.

73,
Gene
W4SZ

Superposition
 

Gene Fuller wrote:
There is no justification for saying that interference causes
superposition or that superposition causes interference or any such
combinations.

That's really good because I didn't say anything like that.
Please don't try to imply that I did.

Superposition can occur with or without interference.

Interference can occur with or without wave cancellation.

If you were to read Born and Wolf you would find that they deal with the
multiple interference problem (antireflective glass) in exactly the same
manner. They never even mention constructive or destructive interference.

I've moved and can't find my Born and Wolf but Hecht certainly
holds constructive/destructive interference in central
position in his classic book. He devotes an entire chapter
to interference.
--
73, Cecil http://www.w5dxp.com

Superposition
 

Gene Fuller wrote:
Cecil Moore wrote:
The constructive interference in free space occurs before
the antennas, not after them. Such is the nature of
constructive interference which very few posters fully
understand. My original posting was designed to expose
the beauty of constructive interference.

That's the best line of the month. Can you help out with the Hollywood
writer's strike? Leno and Letterman need some help.

It's in Born and Wolf, Gene. Too bad you missed it.
Two one watt coherent waves combine with total
constructive interference to a four watt wave.
Of course, somewhere else they combine with total
destructive interference to a zero watt wave so the
average power remains at two watts.
--
73, Cecil http://www.w5dxp.com

Superposition
 

Jim Kelley wrote:
In the case of wave interference , the
words do mean that waves are 'doing things' to other waves.

Thanks Jim, that is exactly what I have been saying
for years. For ideal non-reflective thin-film coatings
on glass, waves are indeed doing things to other waves,
i.e. canceling them.
--
73, Cecil http://www.w5dxp.com

Superposition
 

Cecil Moore wrote:
Jim Kelley wrote:

In the case of wave interference , the words do mean that waves are
'doing things' to other waves.

That should read "In the case of wave interference , the words don't
mean that waves are 'doing things' to other waves."

Thanks for pointing out the typo, Cecil.

73, ac6xg

Superposition
 

Roy Lewallen wrote:
At the points where the fields from the
two antennas completely reinforce, the sum of the fields is 0.7071 +
0.7071 = 1.4142 times the field produced by the original antenna. This
is a field strength gain of 3 dB compared to the original antenna, and
it's a field strength gain, as Antonio says, of 2 (6 dB) compared to the
field produced by each of the two antennas.

That's an example of constructive interference.

At the points where the fields from the two antennas
are equal and 180 degrees out of phase, the sum of the
fields is zero. That's the necessary destructive
interference on the flip side of the coin that satisfies
the conservation of energy principle.

Essentially the same thing happens at a Z0-match in
a transmission line.
--
73, Cecil http://www.w5dxp.com

Superposition
 

Jim Kelley wrote:
That should read "In the case of wave interference , the words don't
mean that waves are 'doing things' to other waves."

If waves are not 'doing things' to other waves, how
are reflected waves eliminated by thin-films on glass?
What happens to the reflection from the thin-film
which has a reflectance of 0.01? If something is
not done to that real reflection, it must still be
there, but we can see that it is not there.
--
73, Cecil http://www.w5dxp.com

Superposition
 

Cecil Moore wrote:
Gene Fuller wrote:
There is no justification for saying that interference causes
superposition or that superposition causes interference or any such
combinations.

That's really good because I didn't say anything like that.
Please don't try to imply that I did.

Superposition can occur with or without interference.

Interference can occur with or without wave cancellation.


Cecil,

Your exact words we

The decrease to zero in reflected energy flow toward the source
is known as "total destructive interference" in the noun version
of the word as used by Hecht. The increase in energy flow
toward the load is known as constructive interference. One need
not refer to superposition as the cause of interference since
the interference *event* implies superposition of two (or more)
coherent waves as the *cause* of the interference *process*.


# Is this not written in English?

# Is there some other interpretation of *cause* in the last sentence?

# Just what do you mean by, "superposition of two (or more)
coherent waves as the *cause* of the interference *process*"?

# Are you playing some sort of word game by using *event* and *process*?

# Do you have a reference for the rules of that word game?


73,
Gene
W4SZ

Superposition
 

Cecil Moore wrote:
Gene Fuller wrote:
Cecil Moore wrote:
The constructive interference in free space occurs before
the antennas, not after them. Such is the nature of
constructive interference which very few posters fully
understand. My original posting was designed to expose
the beauty of constructive interference.

That's the best line of the month. Can you help out with the Hollywood
writer's strike? Leno and Letterman need some help.

It's in Born and Wolf, Gene. Too bad you missed it.
Two one watt coherent waves combine with total
constructive interference to a four watt wave.
Of course, somewhere else they combine with total
destructive interference to a zero watt wave so the
average power remains at two watts.

Cecil,

Sorry. I missed it because it is not there. They don't say any such thing.

73,
Gene
W4SZ