Can both a photon and it's reflection hit a particle?

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Discussion Overview

The discussion revolves around the behavior of a photon emitted towards a particle and its interaction with a mirror. Participants explore concepts related to reflection, interference, and the nature of photons in quantum mechanics, with references to experimental setups like Lloyd's mirror and Fresnel's mirrors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how a reflection can occur if there is only one photon emitted.
  • Another participant suggests that if a photon behaves as a wave, it could potentially reflect off a mirror and hit a particle simultaneously, raising questions about the nature of its path.
  • A participant introduces the concept of Lloyd's mirror interference setup, explaining that a single photon follows one path or the other, and without "which-way" information, the paths can interfere to create a pattern over time.
  • There is a mention of Fresnel's mirrors, which create two virtual sources that could also interfere, although uncertainty remains about whether this has been tested with single photons.

Areas of Agreement / Disagreement

Participants express differing views on the nature of photon reflection and interference, with no consensus reached on whether both the photon and its reflection can simultaneously interact with a particle.

Contextual Notes

Discussions involve assumptions about the behavior of photons as waves and the implications of quantum mechanics, including the concept of "which-way" information and the conditions under which interference occurs.

Crazy Tosser
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So, if you have a mirror and a particle and the source emits one photon, which one hits the particle, the photon or it's reflection in the mirror or both?
 
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If there's only one photon, how is there a reflection? (Ignoring for the moment the meaning of a "reflection" hitting something.)
 
Well, the photon is a wave right? So if it can go through both slits at once, why can't it reflect from the mirror and hit the particle and directly hit the particle at the same time? Or if it can't, why does it go one way or the other way?
 
Are you thinking of something like the Lloyd's mirror interference setup? The source and its image in the mirror act like the two slits in the usual two-slit interference setup. A single photon follows either one path or the other. If there is no "which-way" information, the two paths interfere and you build up an interference pattern on the screen as you send more and more photons through the system, one after the other.
 

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jtbell said:
Are you thinking of something like the Lloyd's mirror interference setup? The source and its image in the mirror act like the two slits in the usual two-slit interference setup. A single photon follows either one path or the other. If there is no "which-way" information, the two paths interfere and you build up an interference pattern on the screen as you send more and more photons through the system, one after the other.

Yes that's exactly what I was thinking of, thank you very much. I didn't know there was an experiment for it.
 
Most optics textbooks describe it, along with a variation called "Fresnel's mirrors" which uses two mirrors to produce two virtual sources that interfere. I don't know if anyone has done a one-photon-at-a-time version.
 

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