I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?
Thanks,
Eric

On Mon, 15 Oct 2012 09:10:47 -0700, etpm wrote:

I was watching a lecture about QED given by Richard Feynman. Part of the
lecture was about the reflection of light. This is what I think he said,
paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the longest
path to a detector, placed anywhere, is equal. However, the AMPLITUDE
of the probability is not equal, but varies. The light particles with
the highest amplitude are the ones we see when the incident angle and
the exit angle are the same, the shortest path. So I think Feynman said
the probablity can be the same but the amplitude of the probability can
be different. Is that correct? If so, can anyone point me to a web site
that explains this in a way a layman can sort of understand?
Thanks,
Eric

Are you sure he didn't mean that the photon was the same everywhere, but
that the amplitude of the probability was different from place to place?

AFAIK, "probability" and "probability amplitude" are the same thing --
either quantum physicists use these terms differently than I'm used to
(possible), or you misheard he said (presumably possible, although I
don't know how many times you listened), or he _meant_ what I'm saying
above (or something similar) but he didn't state it well.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

In article ,
wrote:

I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?

Feynman was stating Fermat's principle, but in a quantum mechanics
framework.

http://en.wikipedia.org/wiki/Fermat%27s_principle

What Fermat actually said was that the actual path is an extremum, which
can be the longest or the shortest. In practice, it's always the
shortest. An extremum is a point where the slope of path length versus
choice of nearby path is zero.

If you want a bigger explanation, try posting the question on sci.optics.

Joe Gwinn

On 10/15/2012 19:10, wrote:
I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct?

He refers to COMPLEX (number) propabilities..

http://en.wikipedia.org/wiki/Quantum...ity_amplitudes

If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?

No.

Kristian Ukkonen.

On Mon, 15 Oct 2012 16:12:08 -0400, Joseph Gwinn
wrote:

In article ,
wrote:

I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?

Feynman was stating Fermat's principle, but in a quantum mechanics
framework.

http://en.wikipedia.org/wiki/Fermat%27s_principle

What Fermat actually said was that the actual path is an extremum, which
can be the longest or the shortest. In practice, it's always the
shortest. An extremum is a point where the slope of path length versus
choice of nearby path is zero.

If you want a bigger explanation, try posting the question on sci.optics.

Joe Gwinn
What I'm asking about Joe is the statement: The probabilities are
equal but the amplitude of the probabilities are not. Is this correct?
I understand that the light can be reflected along longer paths, that
diffraction grating can be used to show this. It's this amplitude
thing that I'm not sure about.
Eric

On Mon, 15 Oct 2012 23:56:48 +0300, Kristian Ukkonen
wrote:

On 10/15/2012 19:10, wrote:
I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct?

He refers to COMPLEX (number) propabilities..

http://en.wikipedia.org/wiki/Quantum...ity_amplitudes

If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?

No.

Kristian Ukkonen.
Thanks Kristian, the link you provided makes sense. I think I get it
now. So even though you said there is no web site you pointed one out
to me. I understand the joke even though I don't really understand
QED. I'll keep plugging away at it though, it's so interesting and
entertaining.
Eric

I have the book. I advise getting one and reading a section - and you
can look it over and over to gain an insight when needed.

Martin

On 10/15/2012 11:10 AM, wrote:
I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?
Thanks,
Eric

In article ,
wrote:

On Mon, 15 Oct 2012 16:12:08 -0400, Joseph Gwinn
wrote:

In article ,
wrote:

I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?

Feynman was stating Fermat's principle, but in a quantum mechanics
framework.

http://en.wikipedia.org/wiki/Fermat%27s_principle

What Fermat actually said was that the actual path is an extremum, which
can be the longest or the shortest. In practice, it's always the
shortest. An extremum is a point where the slope of path length versus
choice of nearby path is zero.

If you want a bigger explanation, try posting the question on sci.optics.

Joe Gwinn
What I'm asking about Joe is the statement: The probabilities are
equal but the amplitude of the probabilities are not. Is this correct?
I understand that the light can be reflected along longer paths, that
diffraction grating can be used to show this. It's this amplitude
thing that I'm not sure about.

Because the probabilities are complex numbers, they can be equal in
magnitude and yet point in different directions. The animated drawing
near Probability Amplitudes in

http://en.wikipedia.org/wiki/Quantum...bility_amplitu
des

gives the general idea.

Joe Gwinn

On Mon, 15 Oct 2012 20:43:28 -0500, Martin Eastburn
wrote:

I have the book. I advise getting one and reading a section - and you
can look it over and over to gain an insight when needed.

Martin

On 10/15/2012 11:10 AM, wrote:
I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?
Thanks,
Eric

That's what I'm gonna do. I have other books by and about Richard
Feynman. Entertaining reading. So now I need to get all of his
lectures in book form that are available. I did find a web site
devoted to these works. Fo someone without a strong math background
the stuff he talks about is a little hard to grasp sometimes. But it
sure is fun!
Eric

It is an interesting read - read the notes in the front of the book -
whence it came - and how and why - Friend, wife and himself!.....

Martin

On 10/16/2012 11:23 AM, wrote:
On Mon, 15 Oct 2012 20:43:28 -0500, Martin Eastburn
wrote:

I have the book. I advise getting one and reading a section - and you
can look it over and over to gain an insight when needed.

Martin

On 10/15/2012 11:10 AM, wrote:
I was watching a lecture about QED given by Richard Feynman. Part of
the lecture was about the reflection of light. This is what I think he
said, paraphrased: When shining a light at a reflective surface the
probabability that the light will take the shortest path or the
longest path to a detector, placed anywhere, is equal. However, the
AMPLITUDE of the probability is not equal, but varies. The light
particles with the highest amplitude are the ones we see when the
incident angle and the exit angle are the same, the shortest path. So
I think Feynman said the probablity can be the same but the amplitude
of the probability can be different. Is that correct? If so, can
anyone point me to a web site that explains this in a way a layman can
sort of understand?
Thanks,
Eric

That's what I'm gonna do. I have other books by and about Richard
Feynman. Entertaining reading. So now I need to get all of his
lectures in book form that are available. I did find a web site
devoted to these works. Fo someone without a strong math background
the stuff he talks about is a little hard to grasp sometimes. But it
sure is fun!
Eric