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I question the double slit conclusion


swift
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I question the conclusion gleaned from the double slit experiment that an electron manifests from a wave like potentia into a real particle. Not that I'm arrogant enough to think I'm right, I question it so that someone may elucidate for me.

 

What is to rule out the possibility that the electron is always a particle which produces a wave like effect because it goes through some kind of deflection (the mechanism of which is currently unknown) which causes it to shoot off at an angle between slit and screen. Perhaps the angle is related to some quantum property of the electron, for instance its momentum. The fact that the momentum can exist in only discrete amounts means the angle exists only in discrete amounts, giving way to areas of darkness on the screen. This makes it look like a wave. Perhaps the greater the momentum, the wider the angle. Perhaps then, the act of detecting the electron by allowing it to pass through a phosphorescent screen (or however it is done) generally reduces the energy and momentum of the electron such that it can no longer be deflected at great angles. Hence, once detection of the electron is made, it is only deflected the minimum amount, ie it appears to go straight on the screen behind, as one would expect a particle to based on our current understanding of particles.

 

How and why the electron is deflected due to it's momentum (or whatever, I simply use that as the first thing that popped into my head) is irrelevant. The point is, what is the argument to logically rule out the idea that there are simply more forces at play that we simply do not know about? I assume there is some way to logically rule out my 'devils advocate' argument above, else physicists jumping to the notion of indeterminate, unreal waves of potentia seems like a bit of a premature leap!

 

Somebody who does physics please help me understand!

 

Also, how exactly do detectors work and how do they physically affect the electron being fired at the slit?

Edited by swift
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I question the conclusion gleaned from the double slit experiment that an electron manifests from a wave like potentia into a real particle.

 

Good for you for questioning it! However, the "wave-like" nature comes from the theory that describes how things behave at that level. The double slit experiment is just one example of that. I don't have time to try and write a longer explanation now, but it might be useful to read a bit of the history of how quantum theory came about....

 

The thing is, how would the defelction by electrons you suggest cause it to form an interference pattern exactly as if it were a wave with the given wavelength?

 

The point is, what is the argument to logically rule out the idea that there are simply more forces at play that we simply do not know about?

 

Science doesn't really work with "things we don't know about". It needs models based on what we do know. But scientists are constantly looking out for "new physics". For example, that is one of the reasons for doing new versions of the double slit experiment; in the hope that it will not match theory and suggest there is something we don't know about.

 

 

I assume there is some way to logically rule out my 'devils advocate' argument above

 

 

I'm not sure there is enough detail to rule it out. Ideas are usually ruled out by making predictions which are tested by experiment. So there doesn't seem any immediate reason to rule it out. But you would need to either show that it explains the evidence better (more accurately or more simply, for example) than current theory or suggest an experiment that would produce a different result if you were right. (Both of these approaches would require quite a lot of maths.)

 

Also, how exactly do detectors work and how do they physically affect the electron being fired at the slit?

 

There was a recent thread on this: http://www.scienceforums.net/topic/86284-particle-detectors/

 

In the case of electrons, I think a phosphor screen is commonly used. But there are many other possibilities.

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If I understood what you wrote, swift, the pattern would emerge even if you pass electrons through a single slit (is there anything that would prevent/modify deflection in that case). You must explain why the pattern hapens even if you release electrons one-by-one and why the pattern changes (disappears) when you close one slit - I am not sure I see that explanation in what you wrote.

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When a wave is directed at a double slit, the slits will effectively act as two new points of origin for the wave on the opposite side of the barrier, and those two waves will interfere with each other, creating a distinctive pattern.

 

A (classical) particle fired at a double slit will go through exactly one of the two slits, and obviously will not interfere with anything because there isn't anything else there.

 

When a single electron is fired through the double slit, it hits a detector screen on the opposite side and we can see where it hits. It's a single point which doesn't have any interference pattern (because how could it if it's just a point?) which you'd expect from a particle. If you keep firing electrons at the double slit one at a time and track the locations, however, an interference pattern emerges as if the probability of the electron landing on any particular spot on the screen was determined by a wave that was interfering with itself after passing through both slits. That wouldn't be terrible surprising with a large number of electrons all fired at once, but the fact that it happens even when firing a single electron at a time men's that each electron must individually be passing through both slits on the way to the detector, not terribly difficult for a wave but very unparticlelike.

 

And we know it's not just some weird deflection pattern as it passes through the slit, because if we only have one slit for the electron to pass through, the interference pattern doesn't present. If the electron was only passing through one of the two slits during the double slit experiment, this shouldn't make any difference, but it does.

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... That wouldn't be terrible surprising with a large number of electrons all fired at once, but the fact that it happens even when firing a single electron at a time mean's that each electron must individually be passing through both slits on the way to the detector, not terribly difficult for a wave but very unparticlelike.

 

And we know it's not just some weird deflection pattern as it passes through the slit, because if we only have one slit for the electron to pass through, the interference pattern doesn't present. If the electron was only passing through one of the two slits during the double slit experiment, this shouldn't make any difference, but it does.

 

I don't think that is a must - rather a possible answer is that the electron passes through both slits...

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"The pattern would emerge even if one slit were covered"

 

That's the answer I was looking for.

 

Thanks!

But AFAICT it's an incorrect answer. One-slit diffraction does not yield the same pattern as double-slit interference. if that's what the answer was implying, then it's wrong.

 

edit: and it's pretty clear that Danijel was merely summarizing your prediction, not confirming that it was correct

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"The pattern would emerge even if one slit were covered"

 

Maybe you are refering to my answer... Maybe I used wrong english... what I ment is "according to your theory, the same pattern would emerge invariably if you have one or two slits open (while in the reality is different)". Therefore I was not supporting your idea. Sorry if I was not clear enough.

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But AFAICT it's an incorrect answer. One-slit diffraction does not yield the same pattern as double-slit interference. if that's what the answer was implying, then it's wrong.

 

We seem to be relying here, on a distinction between "one-slit" and "double-slit".

But when exactly does "one-slit" become distinctly a "double slit"?

 

The distinction is taken as self-evident in most experiments. Because the experiments seem to employ two widely-separated slits. Say for example, two 1-mm slits. Separated by a gap of 10mm.

This gap is big enough, to make the slits clearly two separate entities.

 

So suppose we start the experiment with a single entity - a 1mm slit. And start firing electrons through it. Well, it's just a "single-slit" . So we see "diffraction", but no "interference", yes? So far, so good

 

But now suppose something unexpected happens - an errant spider lands on top of the slit. And the spider descends downwards. Spinning a thread of the finest micrometer-thin silk as it goes. So when the spider gets to the bottom of the slit - the slit has been vertically bisected by the spider's thread.

 

My question is - has this turned the slit into a "double slit"? And will it therefore produce "interference" patterns?

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We seem to be relying here, on a distinction between "one-slit" and "double-slit".

But when exactly does "one-slit" become distinctly a "double slit"?

 

The distinction is taken as self-evident in most experiments. Because the experiments seem to employ two widely-separated slits. Say for example, two 1-mm slits. Separated by a gap of 10mm.

This gap is big enough, to make the slits clearly two separate entities.

 

So suppose we start the experiment with a single entity - a 1mm slit. And start firing electrons through it. Well, it's just a "single-slit" . So we see "diffraction", but no "interference", yes? So far, so good

 

But now suppose something unexpected happens - an errant spider lands on top of the slit. And the spider descends downwards. Spinning a thread of the finest micrometer-thin silk as it goes. So when the spider gets to the bottom of the slit - the slit has been vertically bisected by the spider's thread.

 

My question is - has this turned the slit into a "double slit"? And will it therefore produce "interference" patterns?

One of the assumptions in the double slit interference equation is that the slit separation is large compared to the wavelength of the light (or electron)

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Thanks Swansont. How "large" does the separation have to be? Suppose the separation between the slits is actually smaller than the wavelength of light.

 

Would that create a kind of "second order" diffraction effect?

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Thanks Swansont. How "large" does the separation have to be? Suppose the separation between the slits is actually smaller than the wavelength of light.

 

Would that create a kind of "second order" diffraction effect?

 

You'd have a convolution of the diffraction and interference effects. You can see the diffraction maxima in two-slit interference, if you look for it.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/dslit.html

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Lol. Apologies for that. I did get it, I was just paraphrasing Danijel's answer but didn't want to write the whole thing out: 'If' my theory was correct then "the pattern would emerge with one slit", but it doesn't. Hence, I understand how whatever it is interacts with both slits yet when observed has a singular defined position. Wave to particle.

Edited by swift
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Thanks Swansont. How "large" does the separation have to be? Suppose the separation between the slits is actually smaller than the wavelength of light.

 

Would that create a kind of "second order" diffraction effect?

Dekan, why not buy stuff to perform experiment by yourself... ?

http://www.scienceforums.net/topic/86377-where-to-start-with-quantum-theory/?p=835895

At least with photons and different slits setups..

 

With electrons you would have to have electron gun, and vacuum pump, and f.e. Cockcroft-Walton generator.

 

I have two setups for Young's experiment.

In one slit width 0.05 mm, distance between slits 0.1 mm.

Second one slit width 0.03 mm, distance between slits 0.06 mm. (I just destroyed/damaged it with too powerful blue laser, and it started burning with noticeable smell...)

 

I have several setups for diffraction in single slits, several diffraction granting, several polarization filters..

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  • 1 month later...
  • 3 weeks later...

I question the conclusion gleaned from the double slit experiment that an electron manifests from a wave like potentia into a real particle. Not that I'm arrogant enough to think I'm right, I question it so that someone may elucidate for me.

 

What is to rule out the possibility that the electron is always a particle which produces a wave like effect because it goes through some kind of deflection (the mechanism of which is currently unknown) which causes it to shoot off at an angle between slit and screen. Perhaps the angle is related to some quantum property of the electron, for instance its momentum. The fact that the momentum can exist in only discrete amounts means the angle exists only in discrete amounts, giving way to areas of darkness on the screen. This makes it look like a wave. Perhaps the greater the momentum, the wider the angle. Perhaps then, the act of detecting the electron by allowing it to pass through a phosphorescent screen (or however it is done) generally reduces the energy and momentum of the electron such that it can no longer be deflected at great angles. Hence, once detection of the electron is made, it is only deflected the minimum amount, ie it appears to go straight on the screen behind, as one would expect a particle to based on our current understanding of particles.

 

How and why the electron is deflected due to it's momentum (or whatever, I simply use that as the first thing that popped into my head) is irrelevant. The point is, what is the argument to logically rule out the idea that there are simply more forces at play that we simply do not know about? I assume there is some way to logically rule out my 'devils advocate' argument above, else physicists jumping to the notion of indeterminate, unreal waves of potentia seems like a bit of a premature leap!

 

Somebody who does physics please help me understand!

 

Also, how exactly do detectors work and how do they physically affect the electron being fired at the slit?

 

You make some interesting points. Wave-particle duality is only a best-fit guess and is in no way truly understood. I think it's important and commendable to try and find a better fitting solution and we understand there is possibly some missing information (about anything, from wave-like gravitational distributions under specific conditions, to the induction of entanglement).

Edited by recursion
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I question the conclusion gleaned from the double slit experiment that an electron manifests from a wave like potentia into a real particle. Not that I'm arrogant enough to think I'm right, I question it so that someone may elucidate for me.

 

What is to rule out the possibility that the electron is always a particle which produces a wave like effect because it goes through some kind of deflection (the mechanism of which is currently unknown) which causes it to shoot off at an angle between slit and screen. Perhaps the angle is related to some quantum property of the electron, for instance its momentum. The fact that the momentum can exist in only discrete amounts means the angle exists only in discrete amounts, giving way to areas of darkness on the screen. This makes it look like a wave. Perhaps the greater the momentum, the wider the angle. Perhaps then, the act of detecting the electron by allowing it to pass through a phosphorescent screen (or however it is done) generally reduces the energy and momentum of the electron such that it can no longer be deflected at great angles. Hence, once detection of the electron is made, it is only deflected the minimum amount, ie it appears to go straight on the screen behind, as one would expect a particle to based on our current understanding of particles.

 

How and why the electron is deflected due to it's momentum (or whatever, I simply use that as the first thing that popped into my head) is irrelevant. The point is, what is the argument to logically rule out the idea that there are simply more forces at play that we simply do not know about? I assume there is some way to logically rule out my 'devils advocate' argument above, else physicists jumping to the notion of indeterminate, unreal waves of potentia seems like a bit of a premature leap!

 

Somebody who does physics please help me understand!

 

Also, how exactly do detectors work and how do they physically affect the electron being fired at the slit?

The difference between a particle and a wave is a matter of relative perspective...In a particle, you have momentum and mass, in a wave you have frequency and amplitude....they are both the same thing, depending on how you are viewing them...

 

The trick of the double slit experiment is at the slit...An interference pattern is created and it shows an unclear future unless you observe the particle at the slit...and it makes sense...try to predict where a golf ball is going if you dont see it get hit...you have no information about the golf ball, and the future of how that golf ball is going to end up, after being hit, is random to you...When you look at the golf ball being hit, you then can totally estimate where it is going and where you might find it...depends how good you are at predicting future events, which in the world of non quantum physics can always be done....

 

So...imagine being on a golf course..Youre standing right next to the golfer with your eyes closed....the golf ball is sitting there...when he makes contact with the golfball, that is "the slit"...it is an event which now has a future....you have no clue about that future and the placement of the ball is now unclear to you...it could be many places (a wave)...and it keeps on turning from a golf ball on a tee, into a waveform of unknown results every time it is hit when you arent looking...now just look...you see the golf ball at the moments of impact and every moment after that can be tracked and you see the golf ball and KNOW where it is...so it remained a particle the entire time...If you were a good detector of golf ball movement, you would only need to see the moment of impact (the slit)...you could tell the exact angle and velocity and spin of said golf ball and if your brain were a good computer there would be no question about where the ball would land...

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