Is photon reflection off glass indeterministic?

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So this came up in the Free Will Redux thread, as I was referencing a paper by the physicist Bernard Haisch who in turn is referencing Feynman->

Quote:Feynman discusses this at length in his book QED: The Strange Theory of Light and Matter. He writes:

Quote:Try as we might to invent a reasonable theory that can explain how a photon “makes up its mind” whether to go through glass or bounce back, it is impossible to predict which way a given photon will go.I am not going to explain how the photons actually “decide” whether to bounce back or go through; that is not known. (Probably the question has no meaning.)

Paul offered a counterargument, that in fact photon reflection is not indeterministic...though I can't seem to find the post where he linked a counter explanation at the moment.

So my copy of QED from undergrad is in some used bookstore or secondhand purchaser's hands as that was 10,000 years ago. But I got a new Kindle version and will post more of Feynman's writing. Perhaps it is out of date, though Haisch wrote his own paper in 2014 so he'd also have been guilty of not looking up a correction to the claim that photon reflection is indeterministic...

Anyway should be interesting getting to the bottom of this!
'Historically, we may regard materialism as a system of dogma set up to combat orthodox dogma...Accordingly we find that, as ancient orthodoxies disintegrate, materialism more and more gives way to scepticism.'

- Bertrand Russell


(This post was last modified: 2020-12-31, 07:37 AM by Sciborg_S_Patel.)
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More from QED:


Quote:Try as we might to invent a reasonable theory that can explain how a photon “makes up its mind” whether to go through glass or bounce back, it is impossible to predict which way a given photon will go. Philosophers have said that if the same circumstances don’t always produce the same results, predictions are impossible and science will collapse. Here is a circumstance—identical photons are always coming down in the same direction to the same piece of glass—that produces different results. We cannot predict whether a given photon will arrive at A or B. All we can predict is that out of 100 photons that come down, an average of 4 will be reflected by the front surface. Does this mean that physics, a science of great exactitude, has been reduced to calculating only the probability of an event, and not predicting exactly what will happen? Yes. That’s a retreat, but that’s the way it is: Nature permits us to calculate only probabilities. Yet science has not collapsed.

Feynman, Richard P.. QED: 33 (Princeton Science Library) (p. 19). Princeton University Press. Kindle Edition.


IF Feynman is right it actually gets more interesting, as the percentage of reflection varies with thickness of glass...BUT in a cyclical manner....
'Historically, we may regard materialism as a system of dogma set up to combat orthodox dogma...Accordingly we find that, as ancient orthodoxies disintegrate, materialism more and more gives way to scepticism.'

- Bertrand Russell


If I said that there is no indeterminism involved, then I was wrong. I was trying to distinguish this phenomenon from something like particle decay, where the only thing that matters is the decay factor. Here the energy of the photons, type of glass, thickness of glass, and so forth all matter. Also, an incoming photon can excite photons in the glass, which may happen to travel back toward the source: this isn't reflection at all.

https://physics.stackexchange.com/questi...-off-glass

~~ Paul
If the existence of a thing is indistinguishable from its nonexistence, we say that thing does not exist. ---Yahzi
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(2021-01-01, 12:38 AM)Paul C. Anagnostopoulos Wrote: If I said that there is no indeterminism involved, then I was wrong. I was trying to distinguish this phenomenon from something like particle decay, where the only thing that matters is the decay factor. Here the energy of the photons, type of glass, thickness of glass, and so forth all matter. Also, an incoming photon can excite photons in the glass, which may happen to travel back toward the source: this isn't reflection at all.

https://physics.stackexchange.com/questi...-off-glass

~~ Paul

Ah I may have misinterpreted what you were saying - apologies!

But it does seem there has been discussion on whether this is a truly probabilistic phenomenon, though I do believe that current science maintains some indeterminism remains involved.
'Historically, we may regard materialism as a system of dogma set up to combat orthodox dogma...Accordingly we find that, as ancient orthodoxies disintegrate, materialism more and more gives way to scepticism.'

- Bertrand Russell


(2020-12-31, 08:29 PM)Sciborg_S_Patel Wrote: More from QED:




IF Feynman is right it actually gets more interesting, as the percentage of reflection varies with thickness of glass...BUT in a cyclical manner....
Does it? I thought the thickness of glass affected the absorption of photons within the glass, in other words it affects the transmission rather than reflectance?

(I may have missed something - perhaps this was mentioned in a linked page or article)
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(2021-01-05, 03:21 PM)Typoz Wrote: Does it? I thought the thickness of glass affected the absorption of photons within the glass, in other words it affects the transmission rather than reflectance?

(I may have missed something - perhaps this was mentioned in a linked page or article)

It may be me who has missed something, my physics knowledge has gotten weaker in the 10,000 year interval between now and when I was last in school.

Here's what Feynman says in QED:

Quote:As the thickness of a layer increases, the two surfaces produce a partial reflection of monochromatic light whose probability fluctuates in a cycle from 0% to 16%. Since the speed of the imaginary stopwatch hand is different for different colors of light, the cycle repeats itself at different rates. Thus when two colors such as pure red and pure blue are aimed at the layer, a given thickness will reflect only red, only blue, both red and blue in different proportions (which produce various hues of violet), or neither color (black). If the layer is of varying thicknesses, such as a drop of oil spreading out on a mud puddle, all of the combinations will occur. In sunlight, which consists of all colors, all sorts of combinations occur, which produce lots of colors.

Feynman, Richard P.. QED: 33 (Princeton Science Library) (p. 34). Princeton University Press. Kindle Edition.

Some clarity on this phenomena - where I believe Paul's argument comes in - can be found in this paper ->

Light Partial Reflection Phenomenon

[Fan Xiong, Murat Tanik]

Quote:This paper surveys the strange phenomenon of light partial reflection, and illustrates the probability calculation of this phenomenon with Richard Feyman's quantum electrodynamics theory. The polarization of light with light reflection is also introduced in this paper. The calculation of light reflection intensity is also described in the paper. The relationship of light partial reflection, light polarization and quantum computing is also shortly discussed. This paper will provide people with a thorough background for the basics of light partial reflection and related phenomenon.
'Historically, we may regard materialism as a system of dogma set up to combat orthodox dogma...Accordingly we find that, as ancient orthodoxies disintegrate, materialism more and more gives way to scepticism.'

- Bertrand Russell


(This post was last modified: 2021-01-05, 09:42 PM by Sciborg_S_Patel.)
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  • Typoz
(2021-01-05, 09:30 PM)Sciborg_S_Patel Wrote: It may be me who has missed something, my physics knowledge has gotten weaker in the 10,000 year interval between now and when I was last in school.

Here's what Feynman says in QED:


Some clarity on this phenomena - where I believe Paul's argument comes in - can be found in this paper ->

Light Partial Reflection Phenomenon

[Fan Xiong, Murat Tanik]

Ah, yes, that makes some sense. The mention of the oil film clarified something for me, it is a very thin layer, where the separation between the front and back surfaces is very small. I was thinking of much thicker chunks of glass, such as that in a mirror, the silvering helps of course, but there are separate reflections from front and back surfaces. (As well as some absorption which is really a different topic). The dimensions are much greater than the oil-film or similar.
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