A non-physicist's question on the double-slit experiment

In summary, the argument about the double-slit experiment seems to be unresolved. One side of the argument argues that rate is not a factor, while the other side argues that energy is a significant factor.
  • #1
Quotidian
98
14
OK this question comes from a late-night discussion, er, argument, about the famous double-slit experiment. One of the interesting facts about the double-slit experiment is that the interference pattern that appears on the screen doesn't seem to be affected by the rate at which electrons are fired through the slits. So, even if the electrons (or photons? does it matter?) are fired one at a time, an interference pattern still occurs.

So the question that came up in the argument (and we're all non-physicists, by the way), is whether this means the rate of the discharge of particles doesn't effect the pattern. So whether they're discharged one electron at a time, or at a faster (or is that 'higher'?) rate, then you still get the same pattern.

That was the point of contention in the debate, but none of the participants have enough knowledge of physics to resolve it, so I thought I would bring it here and ask some people who really would know. Thanks.
 
Physics news on Phys.org
  • #2
Quotidian said:
rate of the discharge of particles doesn't effect the pattern.
Correct. The probability of arriving somewhere on the screen is what counts.
 
  • Like
Likes bhobba
  • #3
OK - so you could set up the experiment at various rates, and produce the 'interference pattern', and then send a copy of the patterns to a physicist, and the physicist wouldn't be able to deduce the rate at which the particles were fired?

Also - what is that rate? Is it amplitude, or wattage, or something like that? (Sorry if it's a dumb question.)
 
  • #4
Quotidian said:
OK - so you could set up the experiment at various rates, and produce the 'interference pattern', and then send a copy of the patterns to a physicist, and the physicist wouldn't be able to deduce the rate at which the particles were fired?

Also - what is that rate? Is it amplitude, or wattage, or something like that? (Sorry if it's a dumb question.)
To get the an interference pattern that builds up the individual objects in the 'ensemble' must be identically prepared. A different ensemble, for instance having higher energies per particle, will give a different interference pattern. The gaps/bands will be smaller.
 
  • #5
But you could prepare it in such a way that the interference pattern would remain the same regardless of the rate at which the particles are fired?
 
  • #6
Yes. 24 hours at 1 per second would give the same pattern as 1 second of 86400.
 
  • Like
Likes bhobba
  • #7
Interesting! So energy is a significant variable - if you vary the energy, you vary the resulting pattern - but rate is not. Would that be a valid conclusion, all else being equal?
 
  • #8
Quotidian said:
Interesting! So energy is a significant variable - if you vary the energy, you vary the resulting pattern - but rate is not. Would that be a valid conclusion, all else being equal?
Yes, but only up to the point where the rate is so high that the interaction between different electrons can no longer be neglected.
 
  • #9
Right! But for some range, the effect is independent of the rate. That makes sense.

So, if you don't mind, a related question. Explanations of the double-slit experiment often show interference patterns in water, to convey the idea of what an 'interference pattern' is:

hqdefault.jpg


Would it be possible to emulate the 'rate-independence' of the interference pattern in a water tank? I am thinking that it would not, on the grounds that there is nothing like 'a quantum of water', and so the 'rate' can't be varied in respect of water - only the energy can be varied. Would that be correct?
 
  • #10
Quotidian said:
Would it be possible to emulate the 'rate-independence' of the interference pattern in a water tank? I am thinking that it would not, on the grounds that there is nothing like 'a quantum of water', and so the 'rate' can't be varied in respect of water - only the energy can be varied.
In the water wave analogy, it is the amplitude of the wave that is related to the rate in the QM case, while the frequency of the source producing the wave is related to the energy in the QM case. There is no "one particle at a time" equivalent for a classical wave.
 
  • Like
Likes PeroK
  • #11
Thanks, these replies have been very helpful. The fact that the effect can't be replicated by a physical (water) wave is, I think, due to the interference pattern not actually being 'waves' as such, but something for which the interference patterns of waves is just an analogy.

24 hours at 1 per second would give the same pattern as 1 second of 86400.

The argument that started this was about whether this means that time (being 'rate') is not a factor; which also that means that space (i.e. proximity of particles) is not a factor (as proximity is an aspect of space-time.) So, what is causing the interference pattern is outside, or not a function of, space-time.
 
  • #12
Quotidian said:
The argument that started this was about whether this means that time (being 'rate') is not a factor; which also that means that space (i.e. proximity of particles) is not a factor (as proximity is an aspect of space-time.) So, what is causing the interference pattern is outside, or not a function of, space-time.
Sorry, but this is gobbledygook.
 
  • #13
Can you explain why? It seems to follow, why doesn't it?
 
  • #14
Quotidian said:
The argument that started this was about whether this means that time (being 'rate') is not a factor;
Time is not a factor in the sense that the pattern can be accumulated very slowly. So long as the particles cannot interact with each, it doesn't matter how long it takes one particle to go through the double slit apparatus before the next one enters.

Quotidian said:
which also that means that space (i.e. proximity of particles) is not a factor (as proximity is an aspect of space-time.)
That's a non-sequitur. The fact that time is not a factor has no relation to the fact that space is a factor.

Quotidian said:
So, what is causing the interference pattern is outside, or not a function of, space-time.
This is where the gobbledygook really is. What does it even mean that the "interference pattern is outside space-time"? The particles move in space-time. The double slit and the detector are in space-time. There is nothing outside of space-time. And there is no need to introduce the relativistic concept of space-time to understand or describe anything that is happening here.
 
  • Like
Likes bhobba
  • #15
Well, that was what the argument was about - this is what I came here to resolve. The rate at which the particles are fired doesn't effect the distribution pattern (within limits as explained above). So isn't 'rate' a function of 'time'? So, the particles move in space-time, but the resulting pattern is not affected by the rate at which they're fired.
 
  • #16
Quotidian said:
Well, that was what the argument was about - this is what I came here to resolve. The rate at which the particles are fired doesn't effect the distribution pattern (within limits as explained above). So isn't 'rate' a function of 'time'? So, the particles move in space-time, but the resulting pattern is not affected by the rate at which they're fired. Whatever it is, that is causing the interference pattern is n
A simple way to see it is that it means that each particle is interfering with itself, not with other particles.
 
  • #17
I don't see how that is any less 'gobbledegook' than what I said. Maybe because it is text-book googledegook?
 
  • #18
Quotidian said:
I don't see how that is any less 'gobbledegook' than what I said. Maybe because it is text-book googledegook?
I used the word "gobbledygook" because I think it described well what you wrote. You are using technical terms in a way that does not make sense.
 
  • #19
Thanks. I will try again.

As was said above, '24 hours at 1 per second would give the same pattern as 1 second of 86400'. The output (i.e. distribution pattern) and all other factors are equal. There is only one variable in the scenario, which is 'rate'. So this shows that whatever is causing 'the interference pattern' is not a function of the rate.
 
  • #20
No, the interference pattern does not depend on the rate. (Just to be clear: the interference pattern only becomes apparent when a lot of particles have been measured.)
 
  • #21
That is basically all I wanted to establish, so I won't try and engage in further amateur philosophising about it! But this thread has been very helpful, and thanks for it.
 
  • Like
Likes BvU and bhobba

1. What is the double-slit experiment and why is it important in physics?

The double-slit experiment is a famous experiment in physics that involves passing a beam of particles, such as electrons or photons, through two parallel slits and observing the resulting pattern on a screen behind the slits. It is important because it demonstrates the wave-particle duality of matter, which is a fundamental concept in quantum mechanics.

2. How does the double-slit experiment work?

In the double-slit experiment, a beam of particles is directed towards a barrier with two parallel slits. The particles pass through the slits and interfere with each other, creating a pattern on a screen behind the slits. This pattern is determined by the wave properties of the particles, such as their wavelength and phase.

3. What is the significance of the interference pattern in the double-slit experiment?

The interference pattern observed in the double-slit experiment shows that particles, such as electrons, can exhibit wave-like behavior. This challenges the classical understanding of particles as discrete and localized entities, and instead suggests that they also have wave-like properties. This has important implications for our understanding of the fundamental nature of matter.

4. Can the double-slit experiment be explained by classical physics?

No, the double-slit experiment cannot be fully explained by classical physics. Classical physics assumes that particles are always localized and do not exhibit wave-like behavior. However, the results of the double-slit experiment clearly demonstrate that particles can exhibit wave-like properties, which cannot be explained by classical physics.

5. How is the double-slit experiment relevant to everyday life?

While the double-slit experiment is a fundamental concept in physics, its practical applications may not be immediately apparent. However, understanding the wave-particle duality of matter has led to many technological advancements, such as the development of quantum computers and improved imaging techniques in medicine. Additionally, the principles of the double-slit experiment have also been applied in fields such as optics and acoustics.

Similar threads

Replies
32
Views
2K
Replies
60
Views
2K
  • Quantum Physics
2
Replies
36
Views
1K
Replies
26
Views
1K
Replies
1
Views
959
  • Quantum Physics
Replies
14
Views
1K
Replies
3
Views
750
Replies
5
Views
743
  • Quantum Physics
Replies
4
Views
1K
Back
Top