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Particle wave duality


qft123
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(i) It is not "Juan's definitions" but the standard physicists and chemists definition. And (ii) the quantum definition of particle is not a classical definition.

Which seems to be the crux of the argument. ii more than i, because physicists still discuss classical particles (and perhaps chemists do as well) and in my experience do not make the distinction of calling them classical particles.

 

I can't imagine a non-physicist being satisfied with an answer that an electron is a particle because we've redefined "particle" to mean something that has a combination of classical particle and wave properties. I'm not. I think it's weak, bordering on (or actually being) equivocation. It also doesn't really answer the question of whether there is a wave-particle duality, because the term particle in that phrase is classical. If the answer that's offered is "it's a (quantum) particle" then you've not answered the question.

 

Do quantum particles exhibit behavior like classical waves? How do you answer "no" to that?

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juanrga

In more experimental terms an elementary particle is unambiguously defined by properties such as mass, charge, and spin.

 

studiot

And using Juan's definitions the term particle and elementary particle correspond exactly to the classic definition of the term.

 

 

juanrga

(i) It is not "Juan's definitions" but the standard physicists and chemists definition. And (ii) the quantum definition of particle is not a classical definition. I even stated how one of the properties of a quantum particle (spin) has not classical counterpart.

 

 

Just to be clear why they are the same.

 

Classically a particle (in any branch of physics) is defined as a very small unit or even the smallest unit in which all the property of interest can be considered to be concentrated or considered to act. Particle dimensions are often considered small compared to the dimensions in the problem under consideration.

 

So saying there is a particle which 'carries' spin, mass, charge etc and we make up larger units from these, is in my view, the same thing.

Edited by studiot
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A beam of electrons is not a trajedctory. If it was possible for an electron to follow a classical trajectory precisely then the curve would have a width of zero. The beam width of an eletron beam is very very very far from being a partilce trajectory. If someone is talking about such a trajectorey thn they are ignoring quantumn effects. That's done quite often in classical mechanics but never in quantum mechanics.

 

Let's rephrase the question. Can you make/explain a CRT without invoking QM? I think the answer to that is yes, depending on what precision you are requiring.

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Can you make/explain a CRT without invoking QM?

Yes. Absolutely. A CRT is a macroscopic device and as such doesn't require the principles of quantum mechanics to construct it.

Edited by pmb
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Juanrga is correct in observing that a wave function is not a wave.

 

However we should go further.

 

I said earlier that some behaviour (eg reflection) can be modelled equally well by a stream of particles or by waves.

 

Some behaviour is macroscopic ie the size of the 'particles' is orders of magnitude less than the scale of the phenomenon.

 

My examples of lecher lines and cathode rays are like this. Both the ray and the lecher waves are of a scale that it matters not if the participating 'particles' are little wiggles (wavelets) or little balls.

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It is ironic that a poster uses an old quote from Dirac about wavefunctions for posting attacks to posters who do not buy the duality myth. This poster calls "crackpot science" to what others call modern quantum physics.

 

It is ironic because any modern textbook on quantum physics emphasizes how wrong Dirac was regarding wavefunctions! Yes, textbooks explain how the solutions to the Dirac equation cannot be wavefunctions, in despite that Dirac initially interpreted them as wavefunctions. Dirac was wrong about such wavefunctions, because he missed some advanced aspects of quantum physics. Today we know that the Dirac equation is not a valid wave equation for an electron.

 

I am also perplexed why some posters insist on confounding a wavefunction (i.e. a function without physical meaning) with a wave (i.e. a physical system with physical properties).

 

Since that the wikipedia has been cited. Let us take a look to the talk page:

 

 

A theoretical physicist writes about the wave-particle duality myth:

 

 

In fact, as everyone can check the IUPAC definition of electron do not mention duality and the CERN glossary about modern physics do not mention duality.

 

The quote from Dirac was used becuase it was relevant in the context of your posts where you failed to recognize that even individual/single particles act as waves and that it cannot be dumped as an approximation.

 

I refer two books. One is a textbook "Modern Physics" written by three physicists namely Raymond Serway, Clement J Moses and Curt A. Moyer. I guess this is a prescribed textbook in some universities who want to doa major in Modern Physics and the other book which I refer to is "A begining guide to Quantum Mechanics" by Alastair I.M. Rae where he clearly discusses about the positivism of Bohr.

 

Modern Physics - Raymond A. Serway, Clement J. Moses, Curt A. Moyer

 

They have a seperate sub-section for Wave-Particle Duality and the final note goes like this.

 

Scientists once viewed the world as being made up of distinct and unchangingparts that interact according to strictly deterministic laws of cause and effect. In the classical limit this is fundamentally correct because classical processes involve so many quanta that deviations from the average are imperceptible. At the atomic level, however, we have seen that a given piece of matter (an electron, say) is not a distinct and unchanging part of the universe obeying completely deterministic laws. Such a particle exhibits wave properties when it interacts with a metal crystal and particle properties a short while later when it registers on a Geiger counter. Thus, rather than viewing the electron as a distinct and separate part of the universe with an intrinsic particle nature, we are led to the view that the electron and indeed all particles are amorphous entities possessing the potential to cycle endlessly between wave and particle behavior. We also find that it is much more difficult to separate the object measured from the measuring instrument at the atomic level, because the type of measuring instrument determines whether wave properties or particle properties are observed.

 

In the Questions section they ask this final interesting question which I think is very much relevant here.

 

Are particles even things? An extreme view of the plasticity of electrons and other particles is expressed in this famous quote of Heisenberg: "The invisible elementary particle of modern physics does not have the property of occupying space any more than it has properties like color or solidity. Fundamentally, it is not a material structure in space and time but only a symbol that allows the laws of nature to be expressed in especially simple form."

 

Are you satisfied with viewing science as a set of predictive rules or do you prefer to see science as a description of an objective world of things—in the case of particle physics, tiny, scaled-down things? What problems are associated with each point of view?

 

There is a lot of difference between a particle physicist's view and the positivist view of Bohr which is the accepted consensus. I can send all the particles of a particle physicist through a double slit and get an interference pattern and if there was a field of physicists dealing only with waves they would argue that the wave is real and physical. Now what is the world made up of?

 

Science only deals with observations and that's what it should stick to. Bohr's positivism states that any statement on the nature of the quantum system is metaphysical and it should be treated as meaningless, its ontological. Bohr says that polarisation of a photon is an idealistic concept extrapolated from the results of our observations no greater reality should be attributed to it. This is the accepted consensus.

 

Did Max Born won the nobel prize for giving an incorrect abstract interpretation of the wavefunction?

 

One says the wavefunction is real and physical and the another one says that wave-particle duality is a myth if this is true then why the hell are we teaching the exact opposite of this to physics students?

 

And you quote from the wikipedia: Talk page where any charlatan can claim any nonsense thing. If anyone wants to change the accepted consensus there is a seperate forum for that, if you post it here as though it is an accepted fact it will be called as a crackpot science.

Edited by immortal
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Studiot

Immortal,

I didn't understand the thrust of your post either. I think pmb was simply trying to ask which of the two options you posted you thought was the correct one. I don't think his reply was personalised.

 

As regards to your extract from Dirac, isn't that view superceded by the modern idea of virtual particles?

 

 

 

Immortal

I didn't quoted individually because there were too many posters making speculative claims which contradicts the accepted consensus.

 

 

I don't see how you can call my post speculative, or that it contradicts current concensus.

 

I asked a polite question of your post, offered a friendly comment and then referred to the 2006 Nobel prize.

 

do you intend to answer or avoid discussion?

Edited by studiot
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It is ironic that a poster uses an old quote from Dirac about wavefunctions for posting attacks to posters who do not buy the duality myth. This poster calls "crackpot science" to what others call modern quantum physics.

The wave-paricle duality is no myth. So long as there is a waveklength associated with a particle by

 

[math]\lambda = \frac{h}{p}[/math]

 

the wave-particle duality will have meaning and exist since that's precisly what it means. The term crackpot refers to someone who is crazy or strange. I'd hazard to guess that immortal believes that you're strange for rejecting the heart of quantum mechanics, i.e. the wave nature of particles. Also, when you post quotations without stating the source it doesn't look good.

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Which seems to be the crux of the argument. ii more than i, because physicists still discuss classical particles (and perhaps chemists do as well) and in my experience do not make the distinction of calling them classical particles.

 

A classical particle is a limiting case of a quantum particle. That is the reason which we write "particle".

 

It is worth to mention that some author prefer a different terminology. For instance a quantum chemist writes:

 

Quantum mechanics provides the law of motion for microscopic particles. Experimentally, macroscopic objects obey classical mechanics. Hence for quantum mechanics to be a valid theory, it should reduce to classical mechanics as we make the transition from microscopic to macroscopic particles.

 

Others, including myself, prefer a more standard and logic terminology:

 

classical mechanics <--> quantum mechanics

classical particle <--> quantum particle

 

I can't imagine a non-physicist being satisfied with an answer that an electron is a particle because we've redefined "particle" to mean something that has a combination of classical particle and wave properties. I'm not. I think it's weak, bordering on (or actually being) equivocation.

 

Then you must be objecting to using the term "mechanics" in any discussion of quantum theory with a non-physicist, because in one sense we have redefined "mechanics" and it is no more is a synonym for "classical mechanics".

 

What new terminology do you propose?

 

classical particle <--> wavicle?

classical mechanics <--> ?

 

Do quantum particles exhibit behavior like classical waves?

 

In my first post in this thread I outlined how a classical electromagnetic wave is an approximation to an underlying theory of particles (photons).

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Immortal

 

I don't see how you can call my post speculative, or that it contradicts current concensus.

 

studiot, I never called your post as speculative, my reply was to answer your first question.

 

I asked a polite question of your post, offered a friendly comment and then referred to the 2006 Nobel prize.

 

do you intend to answer or avoid discussion?

 

It was a long time back I read about virtual particles(QED), I did followed and read all the developments of the standard model upto the year 2005 from science reporters here - Science Updates. I am a human and I am ignorant of many things, I cannot know everything. My answer to you is I don't know I'm not an expert, I quoted the excerpt of Dirac because it was relevant here. So when I myself don't know about a subject like QED how can I pretend like I know it. I'll let the experts answer your question and will go and refresh my standard model.

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Do quantum particles exhibit behavior like classical waves?

Not in all cases. E.g. the wave behaviour of quantumn particles is statistical in nature. That means that if we have an experiment which we keep repeating on a single particle and record measurements then the wave nature of the particle will appear when the ensemble is looked at. E.g. No individual particle will exhibit wave bahavioru in this case but the collection of expeiments shows the interference effects by the statistical properties, i.e. particles will have a high probability of gathering near the amplitude of the wave is high. That in no way is classical wave behaviour.

 

I believe that juan has done is to construct a strawman whereby the he created is own interpretation of what the term wave-particle duality means and has argued that his version is a myth. Straw arguments are logical fallacys.

 

In reality it has a particular meaning, found in most QM texts, which is quite correct and is what quantum mechanics is based on. I've sent the real meaning to my fellow posters here so they're well educated on the subject and its true meaning.

 

CERN has a web site about the wave-particle duality

http://choruswww.cern.ch/Public/textes/english/node4.html

Neutrino oscillation

"Neutrino oscillation" is based on what is known as "the wave-particle duality", that is, according to quantum mechanics laws, a particle, when it is propagated, behaves like a wave.

Edited by pmb
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The quote from Dirac was used becuase it was relevant in the context of your posts where you failed to recognize that even individual/single particles act as waves and that it cannot be dumped as an approximation.

 

A particle does not act as a wave. So bizarre as you must find this idea, a particle acts as a particle.

 

The quote from Dirac continues being ironic, because he was wrong precisely regarding wavefunctions, with his wave formulation being an inconsistent formulation.

 

I refer two books. One is a textbook "Modern Physics" written by three physicists namely Raymond Serway, Clement J Moses and Curt A. Moyer. I guess this is a prescribed textbook in some universities who want to doa major in Modern Physics and the other book which I refer to is "A begining guide to Quantum Mechanics" by Alastair I.M. Rae where he clearly discusses about the positivism of Bohr.

 

Modern Physics - Raymond A. Serway, Clement J. Moses, Curt A. Moyer

 

They have a seperate sub-section for Wave-Particle Duality and the final note goes like this.

 

The quote from Serway et al is misleading. The first part of the quote simply remarks that classical physics does not work at the atomic level. This is correct but was emphasized here before.

 

Next Serway et al agree on that an electron is a particle and then write: "Such a particle exhibits wave properties when it interacts with a metal crystal and particle properties a short while later when it registers on a Geiger counter." This phrase is illogical because, by definition, a particle always exhibit particle properties!

 

Their phrase would be more acceptable and rigorous if they did the substitutions "wave properties" --> "classical wave properties" and "particle properties" --> "classical particle properties"; although it would be still open to some fundamental objections.

 

Moreover, if you check their chapter 15, concretely their table 15.2 you would find that the first entry under the row "Particle name" is "electron". Effectively, as any other physicists or chemist, Serway et al define the electron as a particle as well. And so bizarre or crackpot as this idea can seem to some here, a particle acts and behaves as a particle.

 

I can send all the particles of a particle physicist through a double slit and get an interference pattern and if there was a field of physicists dealing only with waves they would argue that the wave is real and physical.

 

There is no real and physical wave in a double slit interference pattern. Only a distribution of particles (plural) that resembles formally the interference pattern of a classical optical wave, but that has a completely different physical interpretation. One time more, (i) the wavefunction is a mathematical function not a real wave and (ii) the state of a particle is given by a wavefunction only as approximation.

 

And you quote from the wikipedia: Talk page where any charlatan can claim any nonsense thing. If anyone wants to change the accepted consensus there is a seperate forum for that, if you post it here as though it is an accepted fact it will be called as a crackpot science.

 

Your anonymous repetitive attacks (including to people who is not here for defending himself) will not change the facts:

 

Sources, speaking on the "duality", either obsolete or are popular, educational, or philosophical literature. Serious contemporary theoretical sources don't mention about duality, they use more effective approaches, almost all based on PI. There is a good analogy with the notion of so-called "relativistic mass", which served its in the interpretation of relativistic effects in terms of Newtonian physics, but in the modern 4-dimensional formulation only creates a confusion Raoul NK (talk) 08:55, 20 September 2010 (UTC)

 

In the same wikipedia page you can read from another editor:

 

but that there is also a confusion between wave-particle duality (implying that an entity like a single electron or a single photon has both particle and wave properties) and the analogy between electromagnetic waves and water waves (to the effect that both consist of particle-like objects but yet collectively show wave behaviour). Although this confusion certainly has played an important role in the history of wave-particle duality, does it seem to me that piling up these different meanings under the same heading does not improve understanding.WMdeMuynck (talk) 10:44, 16 January 2011 (UTC)

 

And if you follow this user (http://www.phys.tue.nl/ktn/Wim/muynck.htm), you find that he has 'some' knowledge in foundations of quantum mechanics.

 

One time again. Our modern picture of the physical world is as follows: Light is made of particles. Atoms are made of particles. Everything in the observable universe is made of particles. Electrons, photons, quarks... are particles. Particles behave as particles.

 

Sometimes a collection of particles behaves collectively as a wave. E.g. a collection of photons under certain restrictions behave as a EM wave, but each individual photon behaves as a particle. A collection of electrons in a double-slit experiment generate a interference pattern that resembles a classical wave, but each individual electron behaves as a particle, following the laws of the quantum mechanics of particles.

Edited by juanrga
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Sometimes a collection of particles behaves collectively as a wave. E.g. a collection of photons under certain restrictions behave as a EM wave, but each individual photon behaves as a particle. A collection of electrons in a double-slit experiment generate a interference pattern that resembles a classical wave, but each individual electron behaves as a particle, following the laws of the quantum mechanics of particles.

That is a not uncommon misconception. An free electron with a well defined momentum has the following associated wavefunction

 

[math]\Psi(x, t) = Ae^{i(kx - \omega t)}[/math]

 

where the wave number k is related to the momentum p through the de Broglie relation

 

[math]p = \hbar k[/math]

 

This is what it means to say that an elecron has wavelike aspects. The wavefunction can scatter off a step potential like a wave can. When a single photon impinges on a double slit its location is localized like that of a particle. But when this reslt is compared to the results of a large ensemble of identical experimental setups the interference pattern appearns but it can't be said that the electrons interact with each other. It is for these reasons, not for the single particle nature of electrons/photons, that there is said to be a wave-particle duality.

 

You have set up a straw arguement whereby you keep repeating what we all klnow very well and purport it to mean that it proves that thre is no wave-particle duality. The error in your straw argument is that nobody is saying that an individual partilce is physically behaving like a wave all by itself. That's not what the wave-particle duality is all about. Its exactly what I just said it was about, i.e. that to every particle there is an associated wavelenth and wavefunction.

 

Straw arguments are logical fallacies and as such are not allowed in the forum.

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Juan

 

How do you explain Quantum Tunnelling with a purely particle concept (I know you don't mean it in the classical sense)?

 

As a consequence of the wave–particle duality of matter, tunnelling is often explained using the Heisenberg uncertainty principle. Purely quantum mechanical concepts are central to the phenomenon, so quantum tunnelling is one of the defining features of quantum mechanics and the particle–wave duality of matter.

 

http://en.wikipedia.org/wiki/Quantum_tunnelling

 

Why is it, wherever I read about W/P Duality, it's never presented in the sense of being an archaic concept which you purport it to be?

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pmb

This is what it means to say that an elecron has wavelike aspects. The wavefunction can scatter off a step potential like a wave can. When a single photon impinges on a double slit its location is localized like that of a particle. But when this reslt is compared to the results of a large ensemble of identical experimental setups the interference pattern appearns but it can't be said that the electrons interact with each other. It is for these reasons, not for the single particle nature of electrons/photons, that there is said to be a wave-particle duality.

 

 

Easy does it!

 

Don't get photons and electrons mixed. I know it applies to both but it is confusing if you swop horses mid race.

 

:rolleyes:

Edited by studiot
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A particle does not act as a wave. So bizarre as you must find this idea, a particle acts as a particle.

 

The quote from Dirac continues being ironic, because he was wrong precisely regarding wavefunctions, with his wave formulation being an inconsistent formulation.

 

Bohr suggested us that we must use classical concepts in redefined abstract way(not literal) to explain our physical experiences with the atomic system. Anyone familiar with QM knows that it is impossible to give a mechanistic description of the events taking place at the atomic level. Bohr said there is no way a quantum object can be described.

 

The quote from Serway et al is misleading. The first part of the quote simply remarks that classical physics does not work at the atomic level. This is correct but was emphasized here before.

 

Next Serway et al agree on that an electron is a particle and then write: "Such a particle exhibits wave properties when it interacts with a metal crystal and particle properties a short while later when it registers on a Geiger counter." This phrase is illogical because, by definition, a particle always exhibit particle properties!

 

 

Their phrase would be more acceptable and rigorous if they did the substitutions "wave properties" --> "classical wave properties" and "particle properties" --> "classical particle properties"; although it would be still open to some fundamental objections.

 

Moreover, if you check their chapter 15, concretely their table 15.2 you would find that the first entry under the row "Particle name" is "electron". Effectively, as any other physicists or chemist, Serway et al define the electron as a particle as well. And so bizarre or crackpot as this idea can seem to some here, a particle acts and behaves as a particle.

 

When no one is observing a quantum object the Copenhagen interpretation says that whether you call it wave properties or particle properties and Kinematic properties or dynamic properties they are not assigned to the quantum object. The properties whether it is of a wave or of a particle is assigned to an object depending on the context of the measuring device and the experimental set up.

 

This is the accepted consensus. Got it?

 

Bohr was a instrumentalist.

 

There is no real and physical wave in a double slit interference pattern. Only a distribution of particles (plural) that resembles formally the interference pattern of a classical optical wave, but that has a completely different physical interpretation. One time more,

 

(i) the wavefunction is a mathematical function not a real wave and

 

 

Correct, I never said that the wavefunction is physical.

 

 

(ii) the state of a particle is given by a wavefunction only as approximation.

 

Incorrect, the wavefunction is symbolic and it doesn't represent anything physical.

 

Your anonymous repetitive attacks (including to people who is not here for defending himself) will not change the facts:

 

Then please quote from reputed source.

 

 

One time again. Our modern picture of the physical world is as follows: Light is made of particles. Atoms are made of particles. Everything in the observable universe is made of particles. Electrons, photons, quarks... are particles. Particles behave as particles.

 

This is wrong, you're claiming too much. QM doesn't allow that, if the property of position and momentum cannot be attributed to a particle before a measurement is being made then even to think of it as a particle is meaningless.

 

Got it?

 

Sometimes a collection of particles behaves collectively as a wave. E.g. a collection of photons under certain restrictions behave as a EM wave, but each individual photon behaves as a particle. A collection of electrons in a double-slit experiment generate a interference pattern that resembles a classical wave, but each individual electron behaves as a particle, following the laws of the quantum mechanics of particles.

 

Again, it depends on the context of the measuring device and experimental set up, QM doesn't allow that.

 

Please stop confusing people around here.

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Easy does it!

 

Don't get photons and electrons mixed. I know it applies to both but it is confusing if you swop horses mid race.

 

:rolleyes:

When I talk about particles scattering off step potentials I can't use photons as an example because they don't interact with step potentials. When I talk about the double slit experiment I use photons since that's what I'm most familiar with in that experiment. That's all.

 

When no one is observing a quantum object the Copenhagen interpretation says that whether you call it wave properties or particle properties and Kinematic properties or dynamic properties they are not assigned to the quantum object. The properties whether it is of a wave or of a particle is assigned to an object depending on the context of the measuring device and the experimental set up.

 

This is the accepted consensus. Got it?

The problem is that he's not acknowledging the associated wavelength of a particle with the particlelike aspects of quantum particles. You'll never get him to acknowledge that fact since he's employing a straw argument which doesn't allow for it.

 

A particle does not act as a wave. So bizarre as you must find this idea, a particle acts as a particle.

We have already pointed out to you that this is not what the wave-particle duality is about. We know all too well that an individual particle is not wave. If it had been then there'd be no wave-particle duality. Please stop arguing a mistake that nobody here has made. I also explained to you that when you use the argument you have, rather then an argument actually pertaining to the wave-particl duality, you commit the logical fallacy known as the straw argument which is defind as follows

straw argument: attacking a straw argument occurs when a weakened imitation of an opponents argument is attacked instead of the opponents original argument because he imitation is easier to refute. The weakened imitation is know as the straw argument.

This is precisely what you do when you claim that an individual particle does not act like a wave. Nobody in this thread has disagreed with that all too simple point. We know that quite well and the fact that you refuse to aknowledge this is quote irritating to all of us as their posts have demonstrated.

 

For the purpose of this thread I propose that we define the wave-particle duality as follows.

 

1) An particle with a well defined momentum has the following associated wavefunction

 

[math]\Psi(x, t) = Ae^{i(kx - \omega t)}[/math]

 

where the wave number k is related to the momentum p through the de Broglie relation

 

[math]p = \hbar k[/math]

 

An arbitrar wave function for a particle is made by summing individual wave functions either by a Forier sers or a Fourier integral.

 

2) From Principles of Quantum mechanics - 2nd Ed. by R. Shankar (graduate level quantum mechanics text), page 113

We found that entities such as the electron are particles in the classical sense in that when detected they seem to carry all their energy, momentum, charge, etc. in localized form: and at the same time that are not particlelike in that assuming they move along definite trajectories leads to conflict with experiment. It appears that each particle has associated with it a wave function [math]\Psi(x, t)[/math], such that [math]|\Psi(x, t)|^2[/math], gives the probability of finding it at a point c at time t. This is called wave-particle duality.

 

All this has been explained to you already and you ignored it and keep repeating yopur straw argumen.

 

Note: To the members of the forum who are participating in this thread, please review the definition I gave for the wave-particle duality and let me know if you object to using it as the definition for the wave-particle duality. Thank you.

Edited by pmb
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Note: To the members of the forum who are participating in this thread, please review the definition I gave for the wave-particle duality and let me know if you object to using it as the definition for the wave-particle duality. Thank you.

 

No, I'm not happy with that definition. I think it is incomplete.

 

Further it implies that the only fundamental entities are particles and that the probability function is somehow 'tacked on' and further that probabilities can only be applied to particles.

 

I am old fashioned and think that it is far better in discussions for the promoter to start off by defining one's terms and the abbreviation symbols used in equations along with any restrictions of application.

 

I always try to address a promoter's terms (not my own) unless I think a genuine mistake has been made.

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No, I'm not happy with that definition. I think it is incomplete.

How so? Can you elaborate? I.e. what would you like to add on to it?

 

Further it implies that the only fundamental entities are particles and that the probability function is somehow 'tacked on' and further that probabilities can only be applied to particles.

It's not intended to address anything except for particles. Sure, there are other things besides particles such as fields. But that doesn't pertain to the wave-particle duality. Each particle has a wave function to it and that wavefunction is interpreted according to its probability density. The definition was never intended to speak about all fundamental entities in quantum theory, only particles and their associate wave property.

 

I am old fashioned and think that it is far better in discussions for the promoter to start off by defining one's terms and the abbreviation symbols used in equations along with any restrictions of application.

As a general rule, I disagree. This is a forum which has several purposes, one of which is to help people learn physics and/or particular aspects of physics. In this case qft123 started a thread to learn about the wave-particle duality, i.e. to learn what the definition is. He couldn't very well have come here to state what something is when his purpose was to learn all about it.

 

I always try to address a promoter's terms (not my own) unless I think a genuine mistake has been made.

For the sake of argument, how would you define the wave-particle duality? How would you have me change the definition that I gave? If I disagree with other people's definitions then that's perfectly fine. I'll just refer to this as my definition. I think it'd be hard to get a definition which we'd all agree on.

 

studiot - Thank you very much for your input.

Edited by pmb
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I think it'd be hard to get a definition which we'd all agree on.

 

I agree.

 

The one fundamental property of a wave is not probability it is periodicity. That is what I would expect to see brought out in any definition employing the use of the word wave.

 

To go further than that it will require some thought.

Edited by studiot
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Juan

 

How do you explain Quantum Tunnelling with a purely particle concept (I know you don't mean it in the classical sense)?

 

As a consequence of the wave–particle duality of matter, tunnelling is often explained using the Heisenberg uncertainty principle. Purely quantum mechanical concepts are central to the phenomenon, so quantum tunnelling is one of the defining features of quantum mechanics and the particle–wave duality of matter.

 

http://en.wikipedia....ntum_tunnelling

 

This question is similar to a previous question by studiot. The answer is the same: using the standard quantum mechanics of particles.

 

Your own link starts with the next definition of quantum tunnelling (bold face from mine)

Quantum tunnelling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount.

 

and in the technical discussion of tunnelling uses (bold face from mine):

The time-independent Schrödinger equation for one particle in one dimension [...] where \hbar is the reduced Planck's constant, m is the particle mass, x represents distance measured in the direction of motion of the particle, Ψ is the Schrödinger wave function, V is the potential energy of the particle (measured relative to any convenient reference level), E is the energy of the particle

 

The rest of the discussion on that page is rather incorrect. For instance who wrote that page interpreted time-independent wave functions as "travelling waves".

 

Why is it, wherever I read about W/P Duality, it's never presented in the sense of being an archaic concept which you purport it to be?

 

Did you read the several quotes and links given before?

Edited by juanrga
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The one fundamental property of a wave is not probability it is periodicity.

A classical wave is defined as any function that satisfies the classical wave equation

 

[math]\nabla^2\Psi = \frac{1}{a^2}\frac{\partial^2\Psi}{\partial t^2}[/math]

 

The general solution is of the form

 

[math]f(x, t) = F(x - at) + G(x + at)[/math]

 

There is no requirement for the wave to be periodic. A wave-packet is a good example of wave which isn't periodic. See details at http://en.wikipedia.org/wiki/Wave_packet

 

The wavefunction in a potential well isn't periodic either.

Edited by pmb
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Bohr suggested us that we must use classical concepts in redefined abstract way(not literal) to explain our physical experiences with the atomic system. Anyone familiar with QM knows that it is impossible to give a mechanistic description of the events taking place at the atomic level. Bohr said there is no way a quantum object can be described.

 

When no one is observing a quantum object the Copenhagen interpretation says that whether you call it wave properties or particle properties and Kinematic properties or dynamic properties they are not assigned to the quantum object. The properties whether it is of a wave or of a particle is assigned to an object depending on the context of the measuring device and the experimental set up.

 

This is the accepted consensus. Got it?

 

Bohr was a instrumentalist.

 

Before, you quoted Dirac on a topic where he was shown to be plain wrong. Now you cite Bohr in another topic where he was wrong. As Steven Weinberg remarks in Physics Today, November 2005, page 31:

 

All this familiar story is true, but it leaves out an irony. Bohr's version of quantum mechanics was deeply flawed, but not for the reason Einstein thought. The Copenhagen interpretation describes what happens when an observer makes a measurement, but the observer and the act of measurement are themselves treated classically. This is surely wrong: Physicists and their apparatus must be governed by the same quantum mechanical rules that govern everything else in the universe.

 

Our understanding of the world has advanced a lot of since Bohr. In last 100 years, we have developed advanced formulations which are very far from the original work by Bohr. We know today that particles always behave as particles with independence of the existence or absence of an observer.

 

(ii) the state of a particle is given by a wavefunction only as approximation.

 

Incorrect, the wavefunction is symbolic and it doesn't represent anything physical.

 

I what wrote is standard quantum physics, whereas what you write is unrelated.

 

One time again. Our modern picture of the physical world is as follows: Light is made of particles. Atoms are made of particles. Everything in the observable universe is made of particles. Electrons, photons, quarks... are particles. Particles behave as particles.

 

This is wrong, you're claiming too much. QM doesn't allow that, if the property of position and momentum cannot be attributed to a particle before a measurement is being made then even to think of it as a particle is meaningless.

 

Got it?

 

Our modern picture of the physical world as made of particles is based in QM. This is the standard vision of the physical world and you are who do not still get it (http://public.web.ce...rdModel-en.html):

 

The theories and discoveries of thousands of physicists over the past century have resulted in a remarkable insight into the fundamental structure of matter: everything in the Universe is found to be made from twelve basic building blocks called fundamental particles, governed by four fundamental forces.
Edited by juanrga
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