To Jim, and anyone else who wants to discuss it. I've created
a graphic illustrating reflections from a thin-film when the
incident laser beam is at an angle to the thin-film surface.

http://www.qsl.net/w5dxp/weblaser.GIF

Question for Jim: I can see Reflection A and Reflection B.
I can measure the irradiance of Reflection A and Reflection B.
Are the two reflections really there or not? If they are there,
do they possess energy and momentum?

That will get us started.
--
73, Cecil http://www.qsl.net/w5dxp

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On Fri, 10 Jun 2005 18:46:47 -0500, Cecil Moore
wrote:
That will get us started.
Rolling on the floor laughing, no doubt.
5 place precision indeed :-)
1000mW in,
20mW reflected,
1010.1mW internal and
1000mW out.

Makes as much sense as Roy's "who's on first base?" math.

Richard Clark wrote:
On Fri, 10 Jun 2005 18:46:47 -0500, Cecil Moore
wrote:

That will get us started.

Rolling on the floor laughing, no doubt.
5 place precision indeed :-)
1000mW in,
20mW reflected,
1010.1mW internal and
1000mW out.

Makes as much sense as Roy's "who's on first base?" math.

You were too quick on the trigger. I copied one of my
article graphics and then decided you are right before
you told me. I removed the extraneous stuff and
simplified it and reposted it to my web page. Please
try again.

http://www.qsl.net/w5dxp/weblaser.GIF
--
73, Cecil http://www.qsl.net/w5dxp

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On Fri, 10 Jun 2005 19:14:32 -0500, Cecil Moore
wrote:

Please try again.
Indeed, as if a million monkeys would eventually write Hamlet....

The laugh-athon continues Roy's "I don't know's on third!" math.

Even with all precision removed (two places is two places too many :-)
the rays show absolutely no evidence of refraction (which makes the
reflections bogus), and the angles are unmarked (which makes the 10mW
labels spurious), and the term irradiance was pulled out of a hat (it
is radiant flux - iff we are to believe anything).

Back to Optical kindergarten.

Richard Clark wrote:
Even with all precision removed (two places is two places too many :-)
the rays show absolutely no evidence of refraction (which makes the
reflections bogus), and the angles are unmarked (which makes the 10mW
labels spurious),

:-) It's a conceptual thought experiment, Richard, not
a cruse missile design.

and the term irradiance was pulled out of a hat (it
is radiant flux - iff we are to believe anything).

Funny that Eugene Hecht, of "Optics" fame, disagrees
with you. "When we talk about the 'amount' of light
illuminating a surface, we are referring to something
called the irradiance, denoted by I - the average energy
per unit area per unit time."

All of Hecht's interference equations are presented
using 'irradiance' not 'radiant flux'. I quote those
equations in my article and possibly in this thread.
That's why I am using 'irradiance'.
--
73, Cecil http://www.qsl.net/w5dxp

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On Fri, 10 Jun 2005 20:54:00 -0500, Cecil Moore
wrote:
a cruse missile design.

ROFL

And eventually this will lead to a balanced energy equation. :-)

Well if there are no places of precision, you are already the
1 million monkeys with white-out.

and the term irradiance was pulled out of a hat (it
is radiant flux - iff we are to believe anything).

Funny that Eugene Hecht, of "Optics" fame, disagrees
with you. "When we talk about the 'amount' of light
illuminating a surface, we are referring to something
called the irradiance, denoted by I - the average energy
per unit area per unit time."
What unit of area? Do your power meters read in Watts/cM² ?
SWR per acre? (or are you metric? SWR per hectare?)

Funny is right
and fame is fleeting when a fan posts your picture - face to the wall.

0% for effort,
10% for Xerox work
0% for graphics
0% for showing work
0% for correctness
-10% for inability to use spell-checker (cruse indeed)
-----
F-

No one expects you to get it right.

Cecil Moore wrote:

To Jim, and anyone else who wants to discuss it. I've created
a graphic illustrating reflections from a thin-film when the
incident laser beam is at an angle to the thin-film surface.

http://www.qsl.net/w5dxp/weblaser.GIF

Question for Jim: I can see Reflection A and Reflection B.
I can measure the irradiance of Reflection A and Reflection B.
Are the two reflections really there or not? If they are there,
do they possess energy and momentum?

That will get us started.

It doesn't show up on my web browser. Do you have the URL right?

If you have a photon zinging through space it posseses both energy and
momentum, and they are each an easy function of the wavelength.

To pick nits, if you have a _stream_ of photons zinging by it will
posess, on average, power and thrust (or whatever the time-derivative of
momentum is called). If reflections A and B are both there they will
each carry a certain amount of power and exert a certain thrust somewhere.

If you have actually set up this thin film experiment and measured two
seperate reflections then they are indeed there. You can debate whether
the reflections are truely reflective of the theory that you're trying
to demonstrate or if they reflect (or perhaps reflect off of?)
imperfections in your experimental setup.

--
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:

Cecil Moore wrote:

To Jim, and anyone else who wants to discuss it. I've created
a graphic illustrating reflections from a thin-film when the
incident laser beam is at an angle to the thin-film surface.

http://www.qsl.net/w5dxp/weblaser.GIF

Question for Jim: I can see Reflection A and Reflection B.
I can measure the irradiance of Reflection A and Reflection B.
Are the two reflections really there or not? If they are there,
do they possess energy and momentum?

That will get us started.


It doesn't show up on my web browser. Do you have the URL right?

If you have a photon zinging through space it posseses both energy and
momentum, and they are each an easy function of the wavelength.

To pick nits, if you have a _stream_ of photons zinging by it will
posess, on average, power and thrust (or whatever the time-derivative of
momentum is called). If reflections A and B are both there they will
each carry a certain amount of power and exert a certain thrust somewhere.

If you have actually set up this thin film experiment and measured two
seperate reflections then they are indeed there. You can debate whether
the reflections are truely reflective of the theory that you're trying
to demonstrate or if they reflect (or perhaps reflect off of?)
imperfections in your experimental setup.


OK, now I can see your post. Yes, those reflections are real, and the
numbers are probably about as good as you'll get from clean AR coated
glass, IFAIK (_dirty_ AR coated glass will give you much larger
reflections). Laser rangefinders get one heck of a return when they
fire, and are limited in the minimum range that they can measure because
of the time that it takes for the receiver to recover (or be turned on,
depending on the LRF architecture).

I'm confused by your confusion -- what are you trying to do, and why do
you have to ask?

--
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:
I'm confused by your confusion -- what are you trying to do, and why do
you have to ask?

I'm not confused. I'm trying to alleviate Jim's confusion. :-)
The next step is to slowly collimate the beam normal to
the thin-film and watch what happens to the reflections. Jim
implies there won't be an internal reflection from surface 'B'
when the beam is collimated. I say it will still be there
possessing energy and momentum. That's the crux of our argument.
--
73, Cecil http://www.qsl.net/w5dxp

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Tim Wescott wrote:

Cecil Moore wrote:
http://www.qsl.net/w5dxp/weblaser.GIF

It doesn't show up on my web browser. Do you have the URL right?

Dang, you guys are fast. You must have caught it just as I was
downloading the simpler version. Please try again.

If you have actually set up this thin film experiment and measured two
seperate reflections then they are indeed there.

I probably could set up that experiment but right now I'm just
talking about it. I'm sure the angle of incidence could be
adjusted until both reflections show up as separate dots on the
retina. How much laser power will burn a retina?

In any case, essentially the same diagram is in any good physics
book. Page 1350 in "Sears and Zemansky's University Physics" by
Young & Freedman, Texas A&M custom edition. Page 505 in "Elements
of Physics" 2nd edition, by Shortley and Williams (c) 1955 :-).
--
73, Cecil http://www.qsl.net/w5dxp

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