Heisenberg's Uncertainty Principle

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Discussion Overview

The discussion revolves around the Heisenberg Uncertainty Principle, particularly focusing on the implications of photon wavelength on the measurement of an electron's position and momentum. Participants explore the relationship between the wavelength of light used in observations and the resulting disturbance to the electron's momentum, as well as the broader implications of the uncertainty principle in quantum mechanics.

Discussion Character

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

Main Points Raised

  • Some participants describe how a photon striking an electron can result in a disturbance of the electron's momentum that is inversely proportional to the wavelength of the light used.
  • It is proposed that using light of a longer wavelength results in a less precise measurement of the electron's position, leading to a blur rather than a sharp point of light.
  • One participant argues that while longer wavelengths disturb the electron's momentum less, they still cause some disturbance, and the degree of disturbance is inversely proportional to the wavelength.
  • Another participant emphasizes that the Heisenberg Uncertainty Principle is not merely a result of disturbances during observations, suggesting a deeper conceptual understanding of the principle.
  • A comparison is made between measuring different components of spin, illustrating how measuring one component can disturb another, akin to the position-momentum relationship in the uncertainty principle.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the disturbance caused by longer wavelengths and the interpretation of the Heisenberg Uncertainty Principle. There is no consensus on whether the principle is solely a consequence of measurement disturbance or if it has a more fundamental basis.

Contextual Notes

Participants discuss the implications of photon wavelength on measurement precision and disturbance, but the conversation does not resolve the nuances of these relationships or the foundational aspects of the uncertainty principle.

shinokk
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When a photon strikes an electron near one of the slits, it bounces (sometimes back at the observer) and registered as a sharp point of light for the observer. In the process, the electrons momentum is disturbed to a degree that is inversely proportional to the wavelength of the light used.

In the next experiment, light of a much longer wavelength is used (in order to strike the electrons with a minimal change in electron momentum). Feynman describes how the photon will bounce to the observer, but will cause a blurry area of light for the observer, rather than a well defined point of light.
Here's how I understand it:
The light of a shorter wavelength disturbs the momentum of the electron, but shows the electron's position.
Why doesn't the light of a longer wavelength disturb the momentum of the electron?
 
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A very similar thread was posted a few days ago.
 
It was, but no one answered it...
 
shinokk said:
Why doesn't the light of a longer wavelength disturb the momentum of the electron?
It also disturbs, but less. How much it disturbs (how much the electron momentum may change) is inversily proportional to the wavelength of the photon.
So - as you determine the electron position (using shorter wavelengths) more precisely, you simultaneously more disturb its momentum.
 
shinokk said:
It was, but no one answered it...

Did you posted that?
Anyway I'll try to explain.

Light of longer wavelength means it has lesser energy and lesser momentum than that of light with shorter wavelength.Consequently it'll not disturb electron's momentum to a greater extent.

When we measure the position of an electron by a photon bouncing off it the best we can do is to estimate its position within one photon wavelength,thus employing a longer wavelength will result in a blurry in electron's position.
 
No, I didn't post it and thank you both for answering. I got the answer I was looking for.
 
shinokk said:
No, I didn't post it and thank you both for answering. I got the answer I was looking for.

The Heisenberg Uncertainty Principle is not a consequence result of disturbance during observations. I hope you don't walk away with that impression.
 
DrChinese said:
The Heisenberg Uncertainty Principle is not a consequence result of disturbance during observations. I hope you don't walk away with that impression.

Could you elaborate on what it means then?
 
Elwin.Martin said:
Could you elaborate on what it means then?

Let's take spin. Suppose you measure a particle's z-component spin and it is always found to be "up", then you can say you have determined its z-component spin precisely. Also, since the result is always the same, this shows that measurement does not necessarily perturb the system. If you now measure its x-component spin, then immediately measure its z-component spin, you will no longer find the same value for the z-component spin. So the measurement of x-component spin disturbs the z-component spin. That is the Heisenberg uncertainty principle for x-component and z-component spin. (It's essentially the same story if you talk about position and momentum.)

This might be helpful:
 
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