On Thu, 30 Jun 2005 11:18:37 -0500, Cecil Moore
wrote:
When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w
Yowza! You, with W's help, can roll your Social Security over into
investments in the CB amplifier Market.
and must be supplied by the sources
[Hecht rolling his eyes] So, this means that Hecht's formula only
works for steady state? :-)
If both are 100W pulses, and the lasers are off before the target are
pulse illuminated -um-
1.) 100W
2.) 200W
3.) 400W
4.) no hundred W
or supplied by destructive interference from somewhere else.
Maybe two more magic lasers?
This is all explained in _Optics_, by Hecht.
Somehow, I don't think so.

How many errors can our readers count?
For N = number of words in orginal posting
errors = N!

Such is the problem of Xerox research.

Richard Clark wrote:

Cecil Moore wrote:
When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

Yowza! You, with W's help, can roll your Social Security over into
investments in the CB amplifier Market.

Note the
following extremely important qualification. The extra power
must come from somewhere, either from the two sources or from
destructive interference. So says Hecht.

When you phasor add 100v to 100v, what V^2/Z0 do you get?

and must be supplied by the sources or or supplied by
destructive interference from somewhere else.

[Hecht rolling his eyes] So, this means that Hecht's formula only
works for steady state? :-)

Yep, irradiance is a quantity averaged over time. It is
steady-state by definition, an accumulated effect.

If both are 100W pulses, and the lasers are off before the target are
pulse illuminated -um-
1.) 100W
2.) 200W
3.) 400W
4.) no hundred W

You will get interference rings of 400w/unit-area and
rings of 0w/unit-area all averaging out to 200w total.
All this is covered in _Optics_. Please spare us your
ignorance and read the book.

If the sources are incapable of supplying the extra power,
For every P1+P2+2*SQRT(P1*P2), i.e. constructive interference,
there is a P1+P2-2*SQRT(P1*P2), i.e. destructive interference.
--
73, Cecil, http://www.qsl.net/w5dxp

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On Thu, 30 Jun 2005 13:28:24 -0500, Cecil Moore
wrote:
You will get interference rings
[Hecht rolling his eyes] for a target that is smaller than a
wavelength?
Must be another failure of Hecht (or Hecht pupil).
of 400w/unit-area and
rings of 0w/unit-area all averaging out to 200w total.
Which, of course, cannot be found in the formula:
Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta)
nor its correction:
Itot = I1 + I2 +2*SQRT(I1*I2)cos(theta)
If the sources are incapable of supplying the extra power,
Which, in the end was a non sequitur.
For every P1+P2+2*SQRT(P1*P2), i.e. constructive interference,
Which, of course, cannot be found in the formula:
Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta)
nor its correction:
Itot = I1 + I2 +2*SQRT(I1*I2)cos(theta)
there is a P1+P2-2*SQRT(P1*P2), i.e. destructive interference.
Which, of course, cannot be found in the formula:
Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta)
nor its correction:
Itot = I1 + I2 +2*SQRT(I1*I2)cos(theta)

When combined with the adhominem (which, of course, reveals another
inaccuracy, one of assignment):
Please spare us your ignorance and read the book.
is possibly the best advice (once the assignment is corrected), given
the continuing goof-ups.

When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

Tor
N4OGW

wrote:

When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

As in coherent RF waves confined to a transmission line, eh?
--
73, Cecil, http://www.qsl.net/w5dxp

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When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w
This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

As in coherent RF waves confined to a transmission line, eh?

That's nothing new. Why do they call them "waveguides" ? Jackson
has a chapter with all the hairy details.

Tor
N4OGW

wrote:

When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

As in coherent RF waves confined to a transmission line, eh?

That's nothing new.

Then why are some of the "experts" on this newsgroup
protesting it so much? Some don't seem to comprehend
the energy situation associated with superposition of
EM fields.
--
73, Cecil, http://www.qsl.net/w5dxp


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On 30 Jun 2005 13:24:55 -0500, wrote:

When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

Hi Tor,

We've seen the math pencil-whipped both ways now to cover all the
available answers. The devil's in the details that are not found in:
Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta)
not to mention the glaring mistakes of the first posting of this
formula.

This is like quoting Einstein's E = MC² (anyone with a Xerox can do
that) and not knowing how much energy it takes to get 100 joules of
green illumination out of a bare lightbulb.

73's
Richard Clark, KB7QHC

When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w

This is correct if the two beams are coherent and have the
same polarization. Very hard to do at optical frequencies, much
easier at lower frequencies.

Hi Tor,

We've seen the math pencil-whipped both ways now to cover all the
available answers. The devil's in the details that are not found in:
Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta)
not to mention the glaring mistakes of the first posting of this
formula.

So? Superposition works. With a yagi antenna, through superposition you
get an EM wave which has larger intensity in certain directions than
for a single dipole with the same power. Someone far away can't tell
the difference between switching to a yagi and turning on a linear.

What the formula doesn't say is that in any real system, the wave
must have a finite extent (not be a infinite plane wave). Then there
must be destructive interference in some directions. So there isn't
a problem with conservation of energy.

Tor
N4OGW