A question about the double slit experiment

[capcom1983]

Is there any evidence that when the electrons pass through the single slit as a wave rather than a particle? Just curious because a single wave should provide the same Pattern as a particle.

 

[mfb]

Modern quantum mechanics does not have "object is a particle" and "object is a wave" as different concepts. A wavefunction of the electron, passing through both slits, is a good (but not the only) description of the system.

 

[capcom1983]

I don't think you understand the question I understand the duality of an electron. I was wondering if when electrons were fired the the single slit ( not the two slits) if there was evidence that they passed through as a wave?

 

[mfb]

Sure, you get single-slit diffraction.

 

[capcom1983]

Yes but is the electron passing through as a particle or wave?

 

[Vanadium 50]

Please reread Post #2, which answers your question.

 

[capcom1983]

What observations have been made of electrons going through the single slit?

 

[fluidistic]

What observations have been made of electrons going through the single slit?

That if the slit is small enough as to be comparable with the de Broglie's wavelength of the electron(s) in question, there will be diffraction.
If you fire the electrons one by one and you have a screen that makes light where the electron hit it and if you mark the spot of where the electrons have hit the screen you'd get a diffraction pattern.
Or if you fire a lot of them at once, you'd see the diffraction pattern shining over your screen.
Edit: See http://arxiv.org/abs/1210.6243v1

 

[Double-Slit]

Is there any evidence that when the electrons pass through the single slit as a wave rather than a particle? Just curious because a single wave should provide the same Pattern as a particle.

Accoring to the Coppenhagen interpretation the electron is a wave until measured.Mathematically we can describe it with a ψ wavefunction,as being a probability distribution of the electron.But physically is a wave until measured.If it's unmeasured it will produce an interference pattern so it will behave like a wave until it hits the screen,then it will become a particle.If it's observed before it enters the slit then it will enter as a particle and will form the 2 strips on the screen.I personally believe that in wave form the electron physically doesn't exists yet only as a wave of probability and it only materializes itself upon interaction,measurement sufficient to cause the quantum decoherence of that wave.

 

[DevilsAvocado]

What observations have been made of electrons going through the single slit?

Many:

https://www.youtube.com/watch?v=KT7xJ0tjB4A


And for a couple of bucks you can try it out yourself:

https://www.youtube.com/watch?v=IS9qAUcoWG8

 

[fluidistic]

DevilsAvocado, photons aren't electrons. :)

 

[DevilsAvocado]

DevilsAvocado, photons aren't electrons. :)

Ouch (need new glasses ;) but they are both best friends of Schrödinger, aren’t they?

https://www.youtube.com/watch?v=ZJ-0PBRuthc

 

[fluidistic]

Nice video, thanks for sharing. Although the OP asked for the single slit (not the double one).

 

[Double-Slit]

Many:

https://www.youtube.com/watch?v=KT7xJ0tjB4A


And for a couple of bucks you can try it out yourself:

https://www.youtube.com/watch?v=IS9qAUcoWG8

What is with the 2nd video's ending (2:28),where the guy says the photon takes every single path from the Moon to Alpha Centauri,he must be kidding,the probability distribution of the photons can't be that big...

 

[DevilsAvocado]

Nice video, thanks for sharing. Although the OP asked for the single slit (not the double one).

No worries mate, I like to quote my dear friend Red Bart – “The slit is in the eye of the beholder”.

 

[DevilsAvocado]

What is with the 2nd video's ending (2:28),where the guy says the photon takes every single path from the Moon to Alpha Centauri,he must be kidding,the probability distribution of the photons can't be that big...

The path integral in quantum-mechanical interpretation

In one philosophical interpretation of quantum mechanics, the "sum over histories" interpretation, the path integral is taken to be fundamental and reality is viewed as a single indistinguishable "class" of paths which all share the same events. For this interpretation, it is crucial to understand what exactly an event is. The sum over histories method gives identical results to canonical quantum mechanics,

 

[crissyb1988]

Accoring to the Coppenhagen interpretation the electron is a wave until measured.Mathematically we can describe it with a ψ wavefunction,as being a probability distribution of the electron.But physically is a wave until measured.If it's unmeasured it will produce an interference pattern so it will behave like a wave until it hits the screen,then it will become a particle.If it's observed before it enters the slit then it will enter as a particle and will form the 2 strips on the screen.I personally believe that in wave form the electron physically doesn't exists yet only as a wave of probability and it only materializes itself upon interaction,measurement sufficient to cause the quantum decoherence of that wave.

Wrong. Even when the electron is observed it will still act like a wave. The only thing that changes is the wavefunction as it collapses into a definite state. This state is still a wavefunction and still acts like a wave. Only difference is that its not a superposition of waves. I any case the OP was talking about a single slit problem NOT double slit.

An electron going through a SINGLE slit whether it is observed or not will produce a diffraction pattern. Observation plays NO role in this particular case. The wavefunction will indeed collapse if we observe but this will not change the pattern we see when we measure. Also its better to think of particles as wavefunctions because they don't suddenly jump from being a particle to then being a wave...

EDIT: Diffraction only occurs when the slit is comparable to the debroglie wavelength

 

[Double-Slit]

Wrong. Even when the electron is observed it will still act like a wave. The only thing that changes is the wavefunction as it collapses into a definite state. This state is still a wavefunction and still acts like a wave. Only difference is that its not a superposition of waves. I any case the OP was talking about a single slit problem NOT double slit.

An electron going through a SINGLE slit whether it is observed or not will produce a diffraction pattern. Observation plays NO role in this particular case. The wavefunction will indeed collapse if we observe but this will not change the pattern we see when we measure. Also its better to think of particles as wavefunctions because they don't suddenly jump from being a particle to then being a wave...

EDIT: Diffraction only occurs when the slit is comparable to the debroglie wavelength

Yes it depends how you interpret particles.If you go by point-like objects in the classical sense then you're wrong because we know it doesn't act like that.A wavefunction will evolve according to the evolution operator until something interferes with it and collapses it to a definite and irreversible state.Whether the previous information is lost or it is preserved in "multiverses" that's a question of debate.In the modern sense we could imagine the particle as being a localized part of a wave while a wave being non-local and propagating through the entire system.The Uncertainty Principle can be much easily understood this way.

On the other hand i`m interested in this experiment,can you explain in detail why the electron doesn't form a stip if measured.Could it be because the edges are less smooth and look like an interference pattern while in reality it is only a strip,or we couldn't track the position of the particle (Uncertainty Principle) like in the 2 slit experiment ,so it will show up as a wave.

 

[crissyb1988]

Yes it depends how you interpret particles.If you go by point-like objects in the classical sense then you're wrong because we know it doesn't act like that.A wavefunction will evolve according to the evolution operator until something interferes with it and collapses it to a definite and irreversible state.Whether the previous information is lost or it is preserved in "multiverses" that's a question of debate.In the modern sense we could imagine the particle as being a localized part of a wave while a wave being non-local and propagating through the entire system.The Uncertainty Principle can be much easily understood this way.

On the other hand i`m interested in this experiment,can you explain in detail why the electron doesn't form a stip if measured.Could it be because the edges are less smooth and look like an interference pattern while in reality it is only a strip,or we couldn't track the position of the particle (Uncertainty Principle) like in the 2 slit experiment ,so it will show up as a wave.

The layman/classical definition of a particle can not be brought into a conversation, and i think (if i read your post correct) we both agree on that. In terms of the scientific definition of a particle I would say that in what ever state, local or non-local, superposition or definite it is still a particle. Whether you observe the particle or not it will still exhibit wave-like properties. Take for example the single slit experiment, observation has no effect on the system. This is because in the double slit we have a superposition of states (ie. particle goes through both slits A and B simultaneously when NOT observed). In the single slit we don't have that kind of superposition. So the resulting pattern for a single slit experiment is a diffraction pattern which appears when the slit width is comparable to the wavelength of the particle. If the slit is too big then we will just see an "image" of a single slit on the screen which is what you are saying. The reason why diffraction happens at all is because waves in general tend to bend around obstacles. So no matter what has happened to a particle it is still a wave.

Ironically diffraction is a classical phenomenon. And as explained in the wiki article all kinds of waves will exhibit these properties
http://en.wikipedia.org/wiki/Diffraction

 

[Double-Slit]

The layman/classical definition of a particle can not be brought into a conversation, and i think (if i read your post correct) we both agree on that. In terms of the scientific definition of a particle I would say that in what ever state, local or non-local, superposition or definite it is still a particle. Whether you observe the particle or not it will still exhibit wave-like properties. Take for example the single slit experiment, observation has no effect on the system. This is because in the double slit we have a superposition of states (ie. particle goes through both slits A and B simultaneously when NOT observed). In the single slit we don't have that kind of superposition. So the resulting pattern for a single slit experiment is a diffraction pattern which appears when the slit width is comparable to the wavelength of the particle. If the slit is too big then we will just see an "image" of a single slit on the screen which is what you are saying. The reason why diffraction happens at all is because waves in general tend to bend around obstacles. So no matter what has happened to a particle it is still a wave.

Ironically diffraction is a classical phenomenon. And as explained in the wiki article all kinds of waves will exhibit these properties
http://en.wikipedia.org/wiki/Diffraction

Totally agreed,but the single slit can be explained also with the uncertainty principle,since with 1 slit we can't detect it's position.So the wavefunction won't collapse.And if you come with an argument that the particle detector will interfere with the system then it won't be enough,like in Einstein's slit thought experiment,the uncertainty is passed on,so the interference must be logical,like in the 2 slit experiment,since it can't be in 2 places when observed because that would violate energy/mass conservation.It's just a matter of point of view whether if you describe it with wave or with particle,but i should guess that the term quantum (pl quanta) is more appropiate than particle.

 

[crissyb1988]

Totally agreed,but the single slit can be explained also with the uncertainty principle,since with 1 slit we can't detect it's position.So the wavefunction won't collapse.And if you come with an argument that the particle detector will interfere with the system then it won't be enough,like in Einstein's slit thought experiment,the uncertainty is passed on,so the interference must be logical,like in the 2 slit experiment,since it can't be in 2 places when observed because that would violate energy/mass conservation.It's just a matter of point of view whether if you describe it with wave or with particle,but i should guess that the term quantum (pl quanta) is more appropiate than particle.

I think you are missing the point completely. the observer has NO effect on the single slit experiment. The particle will act like a wave and particle in BOTH cases (Observed or not). What is stopping us figuring out its definite position in the single slit experiment?

You are correct about the double slit and uncertainty principle.

Quanta is just a property of a particle, it doesn't explain the wave nature. Every physicist will say particle and they will imply, wavefunction with wave-like and classical-particle-like properties. There's no confusion in the scientific community (at least on this simple level).

 

[AkInfinity]

Don't worry kids your queries will be answered soon as I have submited my paper regarding radiation to Arxv: mass of the photon etc...(close to what predicted by debroglie). In response to the OP, no there is no evidence, we have never seen an electron and as feynman we say we can only infer as it is an interpretation. that is the reason why its called the copenhagen interpretation. or example debroglie would say that an electron does pass and has a causal relationship; none of the wavefunction collapes interpretation.

 

[Double-Slit]

I think you are missing the point completely. the observer has NO effect on the single slit experiment. The particle will act like a wave and particle in BOTH cases (Observed or not). What is stopping us figuring out its definite position in the single slit experiment?

You are correct about the double slit and uncertainty principle.

Quanta is just a property of a particle, it doesn't explain the wave nature. Every physicist will say particle and they will imply, wavefunction with wave-like and classical-particle-like properties. There's no confusion in the scientific community (at least on this simple level).

I know that,i didn't said that the observer collapses the wavefunction.It will do that automatically whatever interference collapses it like the uncertainty suggests, if enough information about position is present in the universe (Quantum Information Theory interpretation) it will collapse the wavefunction.By observing here i actually meant just looking at the collected data that's all.

What is stopping us figuring out its definite position in the single slit experiment?

Like maybe the uncertainty principle,as Einstein's slit and box experiment suggests or the Heisenberg microscope experiment,the uncertainty is hereditary to all particles which interact with that system.If a particles position is fully known then we know the one's next to it and then the other's and so on,it would cause a paradox,not to mention that it would evoke a casual observer,some spooky "outside observer" of a kind,and that would be totally nonsense logically.

σ_location*σ_momentum≥ħ/2

The two pairs are derivative conjugates,if one is fully known the other is 1 and it basically means that one of those vectors value or boths must be more then the reduced Planck constant /2.Both can be known but only to a certain extent.I don't like to repeat myself,maybe the measurement is not precise if we measure the particle in the 1 slit example,like i said before it would need a logical barrier (2 slits,so they 100% must be in one place or the other since otherwise it would violate conservation) to know the position by 100%, otherwise see the Einstein's slit,box argument of Heisenberg,the uncertainty will simply pass on to the next particle...
If the not enough information is collected of its path it will produce the interference pattern.In certain cases it could produce a hybrid of the two depending on the existing information,half strip half interference:
http://en.wikipedia.org/wiki/Englert–Greenberger_duality_relation
Thats all :)