Uncertainty Principle: Solving a Problem I'm Having

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Discussion Overview

The discussion revolves around the Heisenberg Uncertainty Principle (HUP) and its implications, particularly in relation to the single slit and double slit experiments. Participants explore their understanding of the principle, its mathematical models, and the experimental observations that illustrate it. The conversation includes conceptual clarifications and personal experiences with the principle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants express confusion about the uncertainty principle, particularly regarding the relationship between position and velocity, and how it applies to measurements.
  • One participant describes the model of using light waves to measure position and the resulting disturbance in velocity, indicating a common understanding of the principle.
  • Another participant references a journal entry that discusses the single-slit diffraction phenomenon as a direct illustration of the HUP.
  • Some participants note the distinction between diffraction and interference in the context of the single and double slit experiments, raising questions about the boundaries between these phenomena.
  • A participant challenges the understanding of the spread of particles when the slit is made smaller, questioning the implications of classical versus quantum mechanics.
  • There is a discussion about the validity of critiques regarding explanations of the HUP, with some participants defending the accuracy of previous descriptions.
  • One participant mentions that the concept of velocity in quantum mechanics is not straightforward and suggests that it is not a meaningful quantity in the same way as in classical mechanics.
  • Another participant proposes that the double slit experiment illustrates the limitations of determining particle paths, suggesting a comparison to other experiments like the microscope experiment.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the HUP and its implications. There is no clear consensus on the interpretations of the experiments or the principles involved, with multiple competing views remaining throughout the discussion.

Contextual Notes

Some statements reflect limitations in understanding the mathematical models and definitions related to the uncertainty principle. The discussion also highlights unresolved questions about the relationship between classical and quantum mechanics, as well as the nature of wave-particle duality.

Spastik_Relativity
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a problem i had recently. I've always thought of the uncertainty principle as if you understand position you less understand velocity and vise versa. the model i know is that to know the exact poition of a particle you shine a light wave on it, the more accurate u want the position the higher frequency you need but the more disturbance in velocity you cause. the problem I am having is my teacher tried to explain in used a single slit light experiment similar to the famous double split experiment. i just didnt quite understand how it works so if anyone could help me with this it would be much appreciated.

thanks
 
Physics news on Phys.org
Someone wrote an amazing explanation of the uncertainty principle that I read on here just a few days back, try searching for it.
 
Single Slit Experiment Resulsts Are Caused By Diffraction Of Light Double Split Experiment Results Are Caused By Interference Of Light
 
Hmm Mmmm
interesting Topic For Pondering .
 
Spastik_Relativity said:
a problem i had recently. I've always thought of the uncertainty principle as if you understand position you less understand velocity and vise versa. the model i know is that to know the exact poition of a particle you shine a light wave on it, the more accurate u want the position the higher frequency you need but the more disturbance in velocity you cause. the problem I am having is my teacher tried to explain in used a single slit light experiment similar to the famous double split experiment. i just didnt quite understand how it works so if anyone could help me with this it would be much appreciated.

thanks

I wrote something about this a while back, but couldn't find the right thread to refer to. So I'll make a reference to my journal entry below:

[11-15-2004 08:26 AM] - Misconception of the Heisenberg Uncertainty Principle

You may want to read this since I used specifically the single-slit diffraction phenomenon to convey the fact that the diffraction effects is the HUP staring at you right on your face.

Zz.
 
Funny Zz, the explanation I was thinking of was your journal entry. Its great, by the way.
 
whozum said:
Funny Zz, the explanation I was thinking of was your journal entry. Its great, by the way.

Then maybe I'm psychic, or I've just invaded your mind. Either way, it's not good!

:)

Zz.
 
ZapperZ, nice expliantion. its definitely helped me further understand the HUP.
 
extreme_machinations said:
Single Slit Experiment Resulsts Are Caused By Diffraction Of Light Double Split Experiment Results Are Caused By Interference Of Light

And where would you draw the line (if there is such a thing) between the 2 classical phenomena...?Give a documented answer.

Daniel.
 
  • #10
dextercioby said:
And where would you draw the line (if there is such a thing) between the 2 classical phenomena...?

i wouldn't know

Give a documented answer.

Daniel.
yes professor...

marlon
 
  • #11
Both phenomena: diffraction and interference are effects of the waves who passes 1 or more splits.
The idea is that the same 'thing' seems TO US to bee a 'wave' some times and a 'particle' some other times.
In fact the concepts of wave and particle are mathematical MODELS in our minds that try to explain what is happening around us (and sometimes do that very well).
The fact is that in this case do not.
The really unpleasant fact is that we are no one intuitive MODEL (and now seems that we will never have) to explain this fact.
 
  • #12
I have read Zapperz's misconception of the Heisenberg uncertainty principle (and in magazines/books etc) and am still confused. What your saying when you describe how when the slit is made smaller the spread of the particles becomes increasingly spread out doesn't makes sense. So you say in classical mechanics you can predict things as accuratly as you want but in quantum mechanics this is not so? So what does this really mean?, what does it imply?
 
  • #13
Beholder said:
I have read Zapperz's misconception of the Heisenberg uncertainty principle ...

I would say that's uncalled for, Beholder. You might try researching the subject before you begin your critique. ZapperZ's description is accurate.
 
  • #14
Beholder said:
I have read Zapperz's misconception of the Heisenberg uncertainty principle (and in magazines/books etc) and am still confused. What your saying when you describe how when the slit is made smaller the spread of the particles becomes increasingly spread out doesn't makes sense. So you say in classical mechanics you can predict things as accuratly as you want but in quantum mechanics this is not so? So what does this really mean?, what does it imply?

You will note that you CAN do this and test it for yourself! I'm not describing something a high-school physics student hasn't seen before. So if you don't think that the pattern you see spreads out as you make the slit smaller, then you have a serious issue with explaining experimental observation.

Also note that arguing against something because it doesn't make 'sense' to you isn't a valid argument in physics. A lot of things do not makes sense until you learn more about it. THEN they make perfect sense. Your "sense" changes with knowledge - it isn't static, nor perfect. The more you know, the more things make sense that didn't used to before. I urge you to never use that to counter something in physics, because frankly, that doesn't make much sense!

Zz.
 
  • #15
Spastik_Relativity said:
a problem i had recently. I've always thought of the uncertainty principle as if you understand position you less understand velocity and vise versa.
That is a statistical principle and does not apply to any single measurement. This applies to more than position and momentum. You mentioned "velocity" but there is no "velocity" operator in QM. Its not a meaningful quantity in QM. One might be tempted to define a velocity operator by dividing the momentum operator by the mass of the particle. However the momentum of the particle is not the mechanical momentum p = mv, its the canonical momentum, which can be different. In fact for an electron moving in an EM field it is different.
... the model i know is that to know the exact poition of a particle you shine a light wave on it, the more accurate u want the position the higher frequency you need but the more disturbance in velocity you cause.
That is correct.
... the problem I am having is my teacher tried to explain in used a single slit light experiment similar to the famous double split experiment. i just didnt quite understand how it works so if anyone could help me with this it would be much appreciated.

thanks
The double slit experiment is often used to show that you can't say which hole the particle went through. What you're speaking of sounds to me very much like an experiment like the microscope experiment. Have you ever read about that one?

Pete
 
Last edited:
  • #16
DrChinese said:
I would say that's uncalled for, Beholder. You might try researching the subject before you begin your critique. ZapperZ's description is accurate.
That's just pure comedy genius! :smile:
 

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