How large is the volume of a photon interacting with matter?

[johaninumea]

When a photon interacts with matter and diffracts, the photon seems to interact with the area of its wave front, determined by an aperture even if it is only one photon. But how far does it interact in depth? Does it always "feel" the whole crystal? Can we assume the photon is reflected by the whole crystal?

 

[BvU]

I'm sorry youtube has its claws in this link, but it's a good treatise

 

[Borek]

Can we assume the photon is reflected by the whole crystal?

Separately shot single photons create interference patterns, so they travel as if they "knew" about whole structure they interact with.

 

[johaninumea]

OK thanks!

 

[sophiecentaur]

Can we assume the photon is reflected by the whole crystal?

The photon must be considered as interacting with everything everywhere because the concept of a photon having an extent does not fit current theory. Of course, in practical terms you only need to consider regions near to the position where the majority of light energy is constrained by conventional optics.
If you truncate the integral that's used in the diffraction calculation then an (sometimes very small) error results.

 

[johaninumea]

Thank you, very well explained! Appreciate this.

I assume though it follows the energy goes with the wave front, so that if would diffract once and then the photon interacts with the crystal a second time, it does not see the whole crystals, is this right?

 

[BvU]

Perhaps it's worth watching the Richard Feynman lectures at University of Auckland

Richard Feynman explains about photons and electrons, including how Feynman diagrams are used (in lecture 3 but don't skip the first 2). An accessible explanation of Quantum Electrodynamics and particle physics (a few details that were uncertain then have been confirmed since). Each lecture is over an hour and then there are excerpts from the question and answer sessions. If you have to teach about Feynman diagrams this gives an excellent insight into how they are used.

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[sophiecentaur]

it does not see the whole crystals, is this right?

UH? It 'sees the whole of the crystal - after all, it's everywhere.

 

[johaninumea]

OK thank you very much to get a better understanding

Johan

 

[johaninumea]

Perhaps it's worth watching the Richard Feynman lectures at University of Auckland


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Thank you for the suggestion!

 

[Swamp Thing]

There were some papers where they showed that one could engineer a screen with, e.g. three slits, such that a wildly non-classical trajectory would make a detectable contribution to the path integral and hence to the detection results. IIRC, an S-shaped path that went through one slit, then doubled back through a second one and finally forwards through a third. Unfortunately I don't have a link.

 

[sophiecentaur]

three slits, such that a wildly non-classical trajectory

IS this with classical wave theory and an actual experiment?

 

[Swamp Thing]

IS this with classical wave theory and an actual experiment?

https://physicsworld.com/a/photons-weave-their-way-through-a-triple-slit/

https://arxiv.org/pdf/1412.2198.pdf

 

[BvU]

Sigh...

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[sophiecentaur]

Sigh...

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Give us a clue - seriously - or was it because PW is only a popular mag?

Trying this experiment with microwaves and a slit antenna (30λ spacing) could easily produce 'sidelobes' at -30dB due to currents induced along the plate. So how would they tell?

 

[BvU]

Give us a clue - seriously - or was it because PW is only a popular mag?

It's ten years old !

But mostly because I was already thinking about all the two-slit dimwits who will use this to happily troll behind. Bit gloomy I grant you.

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