Single slit experiment and HUP

In summary, the conversation discusses how in quantum mechanics, a photon passing through a slit of comparable width will create a Gaussian distribution on a screen. As the slit width decreases, the Gaussian distribution on the screen actually increases, which goes against common intuition. The question posed is whether the slit wall thickness could be the cause of this effect and how it affects the distribution on the screen. The conversation also mentions an applet that demonstrates this phenomenon, but notes that it assumes an infinitely thin wall and does not accurately reflect reality. The conversation also touches on the concept of HUP (Heisenberg's Uncertainty Principle) and its role in the single slit experiment. It is noted that while some view the experiment as validation of HUP, others see
  • #1
Chaos' lil bro Order
683
2
In QM a photon with wavelength comparable to the width of a slit, will pass through and create a 'Gaussian Distribution' on a screen. As the slit width is decreased (gets thinner), the 'GD' on the screen will counterintuitively INCREASE (aka. widen). My question is it possible that the slit wall thicknesses themselves are the cause of this effect? How does slit wall thickness effect the GD on the screen when all other variable are held constant?

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  • #2
With or without HUP as the slit becomes narrower, more of the total light going though it is spread out wider.
How wide can be limited by the thickness of the “wall”. A razor thin wall with a very thin slit say 3 to 4 wave lengths wide, should produce some photons “turning” 600 or more. A full ½-pi turn in theory could be produced by an infinitely thin wall.

For a fun applet on the single and double slits where the screen observations are measured in radians (for a curved screen):

http://www.physics.northwestern.edu/vpl/optics/diffraction.html"

It assumes a infinite thin wall, and allows some light to go through even if the wave length is larger than the slit width, neither of which is realistic, just the formulas to the extremes.
 
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  • #3
RandallB said:
With or without HUP as the slit becomes narrower, more of the total light going though it is spread out wider.
QUOTE]


That experiment is a validation of HUP, so saying with or without HUP is meaningless and makes not sense.
 
  • #4
Chaos' lil bro Order said:
That experiment is a validation of HUP, so saying with or without HUP is meaningless and makes not sense.
NO the idea that the single slit experiment some how provides validation of HUP is what “makes not sense”. You’re not understanding the experiment if you think that.

You get the identical wide distribution of light with lots of photons going thought the one slit together (explain that classically without HUP) as you do when you send one photon at a time though the slit – not so easy to explain that one classically.
A weird and unexplainable result, that HUP is used to explain!
To turn around and then claim the same result you were explaining is proof or validation of the explanation doesn’t cut it.

The only experiments that can be looked at as a validation of HUP-QM are the EPR-Bell proofs. And not everyone agrees that those are conclusive, but the majority do accept them.
Other experiments are just paradoxes resolved by accepting the HUP-QM interpretation.
 
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Question 1: What is the single slit experiment?

The single slit experiment is a classic experiment in quantum mechanics that involves passing a beam of particles (such as electrons or photons) through a narrow slit and observing the resulting diffraction pattern. This experiment helps to demonstrate the wave-like nature of particles and the concept of interference.

Question 2: What is the Heisenberg Uncertainty Principle (HUP)?

The Heisenberg Uncertainty Principle is a fundamental principle in quantum mechanics that states that it is impossible to know the exact position and momentum of a particle simultaneously. This means that the more accurately we measure the position of a particle, the less accurately we can measure its momentum, and vice versa.

Question 3: How is the single slit experiment related to the HUP?

The single slit experiment illustrates the HUP by demonstrating that the more we try to pinpoint the exact position of a particle, the more the diffraction pattern of the particle is spread out, making it more difficult to determine its momentum. This is because the act of measuring the position of the particle disturbs its momentum, and vice versa.

Question 4: What are the implications of the HUP for scientific measurements?

The HUP has important implications for scientific measurements, as it sets a limit on how accurately we can measure certain properties of particles. This means that there will always be a degree of uncertainty in our measurements, and we must take this into account when interpreting our results.

Question 5: Can the HUP be violated?

No, the HUP is a fundamental principle in quantum mechanics and has been demonstrated to hold true for all particles. While it may seem counterintuitive, the HUP is supported by numerous experimental results and is a crucial concept in understanding the behavior of particles at the quantum level.

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