Jim Kelley wrote:
I hadn't seen the one with a 'forward laser power' reading, as if he was
reading it from an SWR meter before. Seems suspicious.

I have presented that example before. You chose not
to discuss it back then. The output of the laser is
given to be one watt. What's so suspicious about that?
Whatever laser one buys comes with a power output
rating.

If we discuss this example, step by step, you can show
me, once and for all, the error of my ways.
--
73, Cecil, http://www.qsl.net/w5dxp

On Thu, 12 Oct 2006 09:56:54 -0700, Jim Kelley
wrote:

a 'forward laser power' reading

Hi Jim,

To quote from an era of scandal:

"Say it a'in't so, Joe!"

.... and I thought the potential for comedy had already drained away.

73's
Richard Clark, KB7QHC

Cecil Moore wrote:

Back to the present thread. I infer that you believe
that Hecht's total irradiance equations are in error?
Before you reply, let me remind you that Dr. Best was
the first one, to the best of my knowledge, to publish
the irradiance equations in an amateur radio
publication, QEX.

In the following fixed font diagram, IR is the Index
of Refraction.

air | 1/4WL thin-film | Glass
1W Laser---IR=1.0---|----IR=1.222-----|--IR=1.493---...
Ifor=1W | Ifor=1.0101W | Ifor=1W
Iref=0.01W | Iref=0.0101W | Iref=0

Note that I is "irradiance", not current.

Given: The irradiance reflection coefficient is 0.01
at both interfaces. The irradiance transmission coefficient
is 0.99 at both interfaces. Please describe your theory of
the wave cancellation process occurring at the air to thin-
film interface without using the superposition and interference
principles that I have been using to which you object.

Cecil,

I don't have a copy of Hecht. Like Jim, I use Born and Wolf as a
"textbook" reference and several other books for practical optical
design reference.

Does Hecht really say that more power goes into the glass than enters
the 1/4WL film? Can we somehow bottle this free energy and save the world?

By the way, those irradiance equations go back a couple hundred years.
It seems unlikely that Dr. Best was the first to publish them, even
considering only amateur-oriented publications.

73,
W4SZ
Gene

Gene Fuller wrote:
Does Hecht really say that more power goes into the glass than enters
the 1/4WL film?

No, and neither did I. The 0.01W of power reflected
in the diagram undergoes destructive interference.
That's why they call it "non-reflective" glass.
The 0.01W is known as the external reflection. There
is a matching 0.01W (not shown) from the internal
reflection that causes wave cancellation. All of this
is explained in any good physics book. If anyone is
willing to go step by step with me, I will either prove
my point or be disproved in the process. What I cannot
figure out is why everyone is avoiding a step by step
technical discussion and instead engaging in ad hominem
comments - hoping to prove what?

By the way, those irradiance equations go back a couple hundred years.
It seems unlikely that Dr. Best was the first to publish them, even
considering only amateur-oriented publications.

Well, I said that was to the best of my knowledge. I
had never seen Ptot = P1 + P2 + 2*SQRT(P1*P2)cos(A)
in an amateur radio publication before and I have
been reading them since 1952.
--
73, Cecil, http://www.qsl.net/w5dxp

On Thu, 12 Oct 2006 18:13:08 GMT, Gene Fuller
wrote:

Does Hecht really say that more power goes into the glass than enters
the 1/4WL film? Can we somehow bottle this free energy and save the world?

Hi Gene,

Isn't this the point at which all should simply surrender to accepting
69% error as being sufficient for a proof? No one here really expects
Cecil's dy-no-mite advantage to be set aside for the sake of accuracy
- do they?

However, your question illuminates the necessity of Cecil being the
one to ask "Where Does the Power Go?" That redeems the thread's
entertainment value.

73's
Richard Clark, KB7QHC

Gene Fuller wrote:
Does Hecht really say that more power goes into the glass than enters
the 1/4WL film? Can we somehow bottle this free energy and save the world?

Gene, here's a complete fixed font irradiance diagram of
the air to thin-film interface including all components.
Reflectance = 0.01, Transmittance = 0.99

Forward irradiance component

Ifor=1W --|
|-- I1=0.99W
I3=0.01W--|

air | thin-film

Reflected irradiance component

|-- Iref=0.0101W
I4=0.01W--|
|-- I2=0.0001W

I1 + I2 + 2*SQRT(I1*I2) = 1.0101W = Ifor in the thin-film
This is "total constructive interference" per Hecht.

I3 + I4 - 2*SQRT(I3*I4) = 0W = Iref in the air
This is "total destructive interference" per Hecht.

Those are the irradiance equations from "Optics", by Hecht.
As Hecht asserts, the destructive interference equals the
constructive interference and the reflections toward the
source are canceled.
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil Moore wrote:
Gene Fuller wrote:

Does Hecht really say that more power goes into the glass than enters
the 1/4WL film? Can we somehow bottle this free energy and save the
world?


Gene, here's a complete fixed font irradiance diagram of
the air to thin-film interface including all components.
Reflectance = 0.01, Transmittance = 0.99

Forward irradiance component

Ifor=1W --|
|-- I1=0.99W
I3=0.01W--|

air | thin-film

Reflected irradiance component

|-- Iref=0.0101W
I4=0.01W--|
|-- I2=0.0001W

I1 + I2 + 2*SQRT(I1*I2) = 1.0101W = Ifor in the thin-film
This is "total constructive interference" per Hecht.

Not exactly as per Hecht. Note to the casual reader: please be
advised that unlike Cecil, Eugene Hecht does not claim that power is
equal to irradiance. Nor does he imply that scaler quantities can be
treated mathematically in the same way as vector quantities, and he
therefore does not substitute power for irradiance in any of his
textbook equations as Cecil has want to do.

These equations do in fact give correct results macroscopically.
However, it is inaccurate to infer from interference equations that a
given electromagnetic wave is 100% reflected from any partially
reflecting boundary. It is only after multiple partial reflections
from the inner boundaries of the intermediate medium that the total
energy from any given wave in conveyed from source to load.

73, ac6xg

Jim Kelley wrote:
Not exactly as per Hecht. Note to the casual reader: please be advised
that unlike Cecil, Eugene Hecht does not claim that power is equal to
irradiance.

It's only fair to tell everyone reading your posting that
you do not accept the definition of power in the IEEE Dictionary
nor the definition of power used by the average RF engineer.
Irradiance, Poynting vectors, and power flow vectors are valid
concepts no matter what esoteric definition of power that you
choose to assert.

Hecht gives the dimensions of irradiance which are the same
as the Poynting vector (power flow vector) in RF engineering.
That you don't consider watts to be power is no reason to
question the validity of irradiance or Poynting vectors.
I don't have "Optics" with me at work so I cannot do an
exact Hecht quote.

Nor does he imply that scaler quantities can be treated
mathematically in the same way as vector quantities, and he therefore
does not substitute power for irradiance in any of his textbook
equations as Cecil has want to do.

I am using Hecht's irradiance equations. Whatever Hecht
implied by those equations is exactly what I am doing. Any
angle used in the irradiance equations is the angle between
the electric fields of the two superposed waves.

It was not me, but Dr. Best, who first substituted power for
irradiance in his series of QEX articles. But Poynting vectors
can obviously be substituted for irradiance since they represent
the same thing and have identical dimensions. Most RF engineers
would assert that Poynting vectors and power flow vectors represent
power. It is your narrow definition of "power" that is the culprit
here, not anything I have said.

If it will make you feel better, forget the power equations and
call them the power flow vector equations. I will try to remember
to do that in the future.

These equations do in fact give correct results macroscopically.
However, it is inaccurate to infer from interference equations that a
given electromagnetic wave is 100% reflected from any partially
reflecting boundary. It is only after multiple partial reflections from
the inner boundaries of the intermediate medium that the total energy
from any given wave in conveyed from source to load.

All the values are average *steady-state* values, the same values
that would be read by a Bird directional wattmeter. All multiple
reflections are rolled into the average Iref value displayed by
the Bird. All multiple forward components are rolled into the
average Ifor value displayed by the Bird.
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil Moore wrote:
Gene Fuller wrote:
Does Hecht really say that more power goes into the glass than enters
the 1/4WL film? Can we somehow bottle this free energy and save the
world?

Gene, here's a complete fixed font irradiance diagram of
the air to thin-film interface including all components.
Reflectance = 0.01, Transmittance = 0.99

Forward irradiance component

Ifor=1W --|
|-- I1=0.99W
I3=0.01W--|

air | thin-film

Reflected irradiance component

|-- Iref=0.0101W
I4=0.01W--|
|-- I2=0.0001W

I1 + I2 + 2*SQRT(I1*I2) = 1.0101W = Ifor in the thin-film
This is "total constructive interference" per Hecht.

I3 + I4 - 2*SQRT(I3*I4) = 0W = Iref in the air
This is "total destructive interference" per Hecht.

Those are the irradiance equations from "Optics", by Hecht.
As Hecht asserts, the destructive interference equals the
constructive interference and the reflections toward the
source are canceled.


Cecil,

Don't bother. I understand the physics quite well, thank you. It is your
message that causes grief. On the other hand, I don't really care to
try to educate you any further, so the grief is quite small.

73,
Gene
W4SZ

Gene Fuller wrote:
Don't bother. I understand the physics quite well, thank you.

So, is anything technically wrong with what I posted?
It is all copied out of various parts of "Optics", by
Hecht.
--
73, Cecil http://www.w5dxp.com