Double-slit experiment and watching the electrons

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Discussion Overview

The discussion revolves around the double-slit experiment, particularly focusing on the effects of "watching" or observing electrons as they pass through the slits. Participants explore the implications of using different light sources, including strong light and long wavelengths, on the interference patterns produced by electrons. The conversation touches on theoretical aspects, mathematical formulations, and experimental considerations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning
  • Experimental/applied

Main Points Raised

  • One participant hypothesizes that using a long wavelength light source with strong intensity might prevent interference due to the inability to determine which slit an electron passes through.
  • Another participant argues that if there is no interaction between the probing light and the electrons, interference will persist, while interaction will eliminate interference.
  • A mathematical model is presented that describes how the probability of detection changes based on the amplitudes associated with each slit, suggesting that interference patterns can vary depending on the quality of which-path information.
  • Some participants express confusion over differing interpretations of the interaction between photons and electrons, with one suggesting that unreliable which-path information might still allow for interference.
  • There is interest in whether experiments have been conducted using strong light sources of long wavelengths and what the outcomes were.
  • One participant mentions previous experiments involving massive projectiles and the potential for varying interference patterns based on detection methods.
  • Another participant describes an experiment using polarizers that demonstrates how interference patterns can change based on the configuration of the polarizers, suggesting a nuanced view of interaction and interference.
  • Several participants express skepticism about the conclusions drawn regarding the interaction of electrons and photons, emphasizing the complexity of phase relationships and their impact on interference visibility.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between interaction, which-path information, and interference patterns. Some argue for a clear distinction between interacting and non-interacting scenarios, while others suggest a more nuanced approach where partial coherence and unreliable information can still yield interference. The discussion remains unresolved with multiple competing interpretations present.

Contextual Notes

Limitations include the dependence on definitions of interaction and which-path information, as well as unresolved mathematical formulations. The scope of the discussion is restricted to theoretical and experimental considerations without definitive conclusions.

  • #31
Do you know if S M TAN is Shina Tan? He looks very young.
 
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  • #32
naima said:
Do you know if S M TAN is Shina Tan?

No. S M Tan is Sze Meng Tan.
 
  • #33
thank you.
There is a 3/2 factor in the visibility formula. From which identity does it come?
 
Last edited:
  • #34
We begin with an integral from zero to pi of a function of the angle \theta.
Using x = cos (\theta.) visibility of the fringes becomes
A\int_{-1}^1 (1+x^2) e^{i u x} dx.
Integrating it twice by parts we get
4A [\frac{sin u}{u}+\frac{cos u}{u^2}-\frac{sin u}{u^3}].
"u" being the distance of slits divided by the wavelength of the photon when it decreases to zero the limit of visibility must be 1. We need so a normalization factor and the good formula is
3/2 [\frac{sin u}{u}+\frac{cos u}{u^2}-\frac{sin u}{u^3}].

We can compute the visibility when u = 1. It is when we watch the electrons with light having for wavelength the distance
between the slits. We have V(1) = 3/2 cos(1) = 0.8
So the visibility is still very good!
 
Last edited:

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