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Particle wave duality


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I found where Feynman explains in QED that electrons have a wave-like property. It's on page 84.

In 1924 Louis de Broglie found that there was a wavelike character associated with electrons, and soon afterwards, C.J. Davisson and L.H. Germer of Bell Laboratories bombarded a nickel crystal with electrons and showed that they, too, bounced off at craxy angles (just like X-rays do), and that these angles could be calculated from De Broglies formula for the wave-length of an electron.

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! Moderator Note pmb, Please stop derailing the thread. If you wish to discuss it, you know what to do.

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"Wave-particle duality" is often a misleading name. Electrons and photons are quantum mechanical particles. They do not behave in the same way that classical particles do, and indeed can't really be e

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The obvious conclusion is that both the corpusculer and wave models are inadequate by themselves and that the true nature is something with some of the characteristics of both plus perhaps properties we have yet to uncover.

 

Why is this so hard to swallow?

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The obvious conclusion is that both the corpusculer and wave models are inadequate by themselves and that the true nature is something with some of the characteristics of both plus perhaps properties we have yet to uncover.

 

Why is this so hard to swallow?

Wonderful. Well said sir!! So well put that it brings a tear to me eye! :P

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The obvious conclusion is that both the corpusculer and wave models are inadequate by themselves and that the true nature is something with some of the characteristics of both plus perhaps properties we have yet to uncover.

 

Why is this so hard to swallow?

 

Well said indeed.

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everything in the Universe is found to be made from twelve basic building blocks called fundamental particles, governed by four fundamental force.

 

And just how many times in the past have scientists and thinkers made this claim that they know everything?

 

Mendelev and his mates were wrong about the number of elements

 

Kelvin was wrong about the cooling of the earth....

 

I suggest that anyone making such an extravagant claim is suffering from a severe case of bloaty head.

 

Neither CERN scientists nor myself are saying that we know everything. We are saying something very different. We are saying that everything in our universe "is found to be made" from a small number of known particles. The link given above lists the known particles: electrons, quarks, photons, neutrinos, muons, gluons... Their glossary is also interesting

 

http://public.web.ce...ossary-en.php#P

 

The scientific fact is that all known phenomena up to the date can be explained with a quantum theory of particles.

 

I repeat: the above CERN quote is about that we have found.

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The scientific fact is that all known phenomena up to the date can be explained with a quantum theory of particles.

 

Dark matter isn't predicted by the standard model, and it's more than reasonable to think that DM may consist of particles.

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The scientific fact is that all known phenomena up to the date can be explained with a quantum theory of particles.

 

Dark matter isn't predicted by the standard model, and it's more than reasonable to think that DM may consist of particles.

 

The above quote says "a quantum theory of particles". The Standard Model is only a subset of "a quantum theory of particles". What is more, the section "So far so good, but..." in the CERN link given by me before --in this same thread-- explains what are the limits of the Standard Model.

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Sorry qft123. I intended that to show the nature of the wave-particel duality. In principle the double slit experiment doesn't work just for photons. Theoretically you can defract electrons through a double slit too. It's just way too impractical. However, in 1928 Davisson and Germer did a similar experiment whereby electrons were scattered from the surface of nick crystals and a diffraction pattern was formed. The wonderous thing about this is that they discovered this phenomena by an accident. Cool, huh? :P

Yeah, pretty much. Thanks for the knowledge.

Even X-Rays were discovered by an accident, but let's not get off topic.

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Particle wave duality is a myth, which arose in the early times of quantum mechanics when only classical particles or classical waves were known and the myth was born to try to explain the experiments where the objects under study did not behave as classical particles or classical waves. The idea that photons sometimes behave as waves and sometimes behave as particles is a recurrent, but completely incorrect, claim.

 

It's also a straw man. If you say photons, you are already acknowledging the particle-like behavior. A proper formulation of the statement would be that light sometimes acts like a wave and sometimes like a particle.

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It's also a straw man. If you say photons, you are already acknowledging the particle-like behavior. A proper formulation of the statement would be that light sometimes acts like a wave and sometimes like a particle.

 

I thought it was about measurement: when you measure it in order to prove it is a particle, you find it is a particle, and when you measure it in order to prove it is a wave, you find it is a wave.

 

In my simple mind governed by prehistoric logic, since a macroscopic wave is a kind of phenomena build from a bunch of smaller things, maybe the photon is not a single fundamental particle, but the result of a bunch of interacting things (ROABOIT). Hit me.

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Dark matter isn't predicted by the standard model, and it's more than reasonable to think that DM may consist of particles.

Also, I wouldn't say that the properties of spacetime couldn't be explained by QM. E.g. nobody has ever used QM to derive the expression for time dilation or length contraction. Black holes can't be explained by QM either. Myself, I never use wide sweeping generalizations like that. There are always exceptions to every rule such as the ones I mention here.

 

I thought it was about measurement: when you measure it in order to prove it is a particle, you find it is a particle, and when you measure it in order to prove it is a wave, you find it is a wave.

Young's double slit experiment is a good example of the wave-particle duality. If you set up an ensemble of such experimental set ups and let just one photon go through the double slit and then compare all the results then (1) in each individual set up you'll see that only a single photon is detected on the screen and (2) the collected results will show the interference phenomena. It's pretty cool! :P

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A proper formulation of the statement would be that light sometimes acts like a wave and sometimes like a particle.

 

A proper and modern picture was given: Light is made of particles named photons. Under certain circumstances a collection of photons behaves, collectively, as something that we call a wave. The wave theory is an approximation to the underlying quantum theory of particles.

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I collect 10$ from everyone who fallaciously says that to me.

 

:rolleyes:

Do you except cyberbucks? If so then here {cha-ching! - $11.00}. I added a doller for prompt service. :P

 

A proper and modern picture was given: Light is made of particles named photons. Under certain circumstances a collection of photons behaves, collectively, as something that we call a wave. The wave theory is an approximation to the underlying quantum theory of particles.

The wave characteristics of particles also applies to single particles. When a single particle approaches a step potential part of the wave is transmitted and part is relfected. That's the wave character manifesting itself. A wave function can apply to single paricles. A wave can be a continuous superposition of waves to give a wave packet too. That wave packet can scatter off of a point potential like the potential associated with a nucleus.

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Juan,

I would be interested to hear your corpusculer explanation of lecher lines.

 

In the first place I am always writing about particles, because elementary particle is a technical term with an unambiguous definition in physics and chemistry. 'Corpuscules' is not.

 

In the second place, I already said in #10 that wave theory is an approximation. Textbooks explain how to obtain EM wave theory as an approximation to the underlying theory of particles such as the electron and the photon.

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Note: When we, physicists and chemists, affirm that everything is found to be made of particles, we mean everything.

 

Everything includes atoms, molecules, nuclei, lecher lines, waveguides, distant stars, electrons in Young experiment, electrons in high energy accelerators, lions, volcanoes, the Moon...

 

The wave particle duality is a myth, an old and persistent myth. Advanced and rigorous treatments do not even mention this myth, except maybe in the introductory chapter devoted to the historical roots.

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I asked a simple, polite question.

 

I used the word corpusculer to allow the freedom to introduce any particle or particles you choose since corpuscule is a very well defined term. It is more general than 'particle' since it allows possibility of yet undiscovered particles or particle properties.

 

I also used it since you like to appeal to authority, and I regard Newton as having greater intellect and authority than you or I or all the people at CERN put together.

 

So I repeat.

 

Please explain the operation of lecher lines in terms of corpuscles (substitute any particle or particles you choose).

Edited by studiot
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I used the word corpusculer to allow the freedom to introduce any particle or particles you choose since corpuscule is a very well defined term. It is more general than 'particle' since it allows possibility of yet undiscovered particles or particle properties.

 

I also used it since you like to appeal to authority, and I regard Newton as having greater intellect and authority than you or I or all the people at CERN put together.

 

I did not appeal to authority, and when I cite references (which, at the other hand, is not something unusual in a scientist) I do because I do not want to waste time writing something already written somewhere.

 

You regard Newton as having a greater authority than people working at CERN. I disagree.

 

You must believe that "yet undiscovered particles or particle properties" are required to explain something so trivial as lecher lines, but that is completely untrue. As I already said in #40, EM wave theory is a well-defined approximation to the current quantum theory of particles.

Edited by juanrga
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So once again I say you are unable to explain lecher lines in terms of particles and thereby prove your claim.

 

I asked a civil question which you keep dodging.

 

I freely admit that I cannot do it because I do not believe that such an explanation exists or can be made.

 

However I would still be interested if one can be made.

Edited by studiot
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So once again I say you are unable to explain lecher lines in terms of particles and thereby prove your claim.

 

You can repeat it so many times like you want, but I do not care because I know that:

  1. Lecher lines will continue to be explained in terms of particles, because, as said to you before, EM wave theory is a well-defined approximation to a quantum theory of particles.
  2. The CERN site will continue to say that everything is found to be made of particles, because this is an experimental fact.
  3. Both CERN and IUPAC will continue to define the electron as a particle, because our more modern and sophisticated model of the world is a theory of particles.

Edited by juanrga
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studiot - It's not just EM waves that are quantized. The electromagnetic field itself is quantized, even when the field is static.That's what Quantum Field Theory (QFT) is all about. See http://en.wikipedia.org/wiki/Quantum_field_theory

 

Also, while its quite true that electrons are called particles it doesn't mean that they behave like a particles.

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pmb, I was not referring to electromagnetic anything. I was referring to copper wires and light bulbs, although voltmeters would do they are not so spectacular.

 

I don't need QFT to explain a real physical effect any more than I need it to explain why my table is holding up my computer as I type.

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