Difference between probability waves & electromagnetic waves?

[sasan]

What I know: A ripple/wave in a field gives rise to a particle. For example, a ripple in electric field creates a photon.

Question: Is this the same principle as probability wave which when observed reveals a particle?

 

[mfb]

No, the two things have nothing in common.

 

[sasan]

If you are right, then Sean Carroll must be wrong in this video at Fermi Labs:

please see 29:50

A minute later he says a camera can also collapse the wave function. And this is also wrong.

 

[sophiecentaur]

No, the two things have nothing in common.

If you consider the De Broglie approach to how particles with mass behave in some circumstances then is there an essential difference? The famous two slits experiment works for em waves and beams of particles so there is quite a lot of 'waviness' in common - at least in as far as they two things can be analysed.
I do have a problem with the use of the word 'particle' to classify photons because they do not behave like little bullets. (Feynman is a bit responsible for people thinking that but he did know better - his Feynman Diagram is partly to blame.)That video above suggests that they do - but he has a few weasel words to distance himself from actually committing all the way along that road.
But arguments about 'what things really are' will seldom get us anywhere - that also can apply to 'what things really are not'. It always depends how you happen to be looking at things.

 

[mfb]

If you are right, then Sean Carroll must be wrong in this video at Fermi Labs:

I don't understand why you think this would contradict what I said.

A photon does not even have a well-defined position, by the way. You can have a "ripple in the electromagnetic field" that is a photon - but you can't assign a proper nonrelativistic wave function or a position to it.

 

[sophiecentaur]

You can have a "ripple in the electromagnetic field" that is a photon

Do you have a reference to that description? I thought that the modern interpretation is that the photon is only regarded as having presence when it is interacting with a charge. Otherwise, the power flows as a wave. A "ripple" implies some location and that is a questionable model.

 

[mfb]

Do you have a reference to that description?

It is the fundamental idea of quantum field theory. Every textbook covers it.

I thought that the modern interpretation is that the photon is only regarded as having presence when it is interacting with a charge.

You can have an electromagnetic field without any charges. It won't do anything interesting then, but quantum field theory without interactions is the easiest case.

Otherwise, the power flows as a wave.

What does that mean?

A "ripple" implies some location and that is a questionable model.

A region where some ripple is: Yes. A specific location: No.

 

[sophiecentaur]

You can have an electromagnetic field without any charges.

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Yes but that's not what I was talking about. Of course the situation in which Power is being transferred can be described as waves (changing fields) but the interaction between that wave and a charge system is where the photon becomes involved. That term 'ripple' (I read a few places where the term is used) is well chosen as it doesn't actually suggest a precise location but rather a 'region' which could be the size of a football field or an atom (which is fine). Unfortunately, it can be misinterpreted as a very tightly defined region (=location) and that is how the word 'particle' is often interpreted.

It won't do anything interesting then

Yes. It's only when there is a charge system that anything 'interesting happens'.
Are we disagreeing?

 

[hilbert2]

What I know: A ripple/wave in a field gives rise to a particle. For example, a ripple in electric field creates a photon.

Question: Is this the same principle as probability wave which when observed reveals a particle?

The electromagnetic field consists of two vector fields, while a Schrödinger wave function is a single scalar field. A massless particle like a photon can't be described with a Schrödinger wave function, you need relativistic QFT for that. Also, in relativistic quantum field theory, fermionic particles like an electron or positron are obtained by quantizing a Dirac field that is neither a scalar or a vector field, but a spinor field.

 

[sophiecentaur]

The electromagnetic field consists of two vector fields, while a Schrödinger wave function is a single scalar field. A massless particle like a photon can't be described with a Schrödinger wave function, you need relativistic QFT for that. Also, in relativistic quantum field theory, fermionic particles like an electron or positron are obtained by quantizing a Dirac field that is neither a scalar or a vector field, but a spinor field.

The OP was asking about the basic principle, rather than details of the fields involved. Sasan is not 'confusing' the two, imo. There is a lot of equivalence - even if only at the mathematical level.

 

[hilbert2]

The OP was asking about the basic principle, rather than details of the fields involved. Sasan is not 'confusing' the two, imo. There is a lot of equivalence - even if only at the mathematical level.

Ok, my bad. I just though that it's good to point out how many different kinds of fields there are. On a second thought, the wave function in time dependent Schrödinger equation can be interpreted as a classical field too, and quantized similarly to the EM and fermion fields (I guess that description has some use in condensed matter physics).

 

[sasan]

Thank you all for replying. The reason I asked this question: There is HUGE confusion among people including scientists as to what is particle-wave duality?

The duality is that light behaves like a wave (refraction and detraction, for example) and sometimes like a particle (the photoelectric effect). But many people think particle-wave duality has to do with the wave-function that collapses into a particle.

So in a sense matter has dual duality!

Do you see my point? Please let me know.

 

[sophiecentaur]

what is particle-wave duality?

It's a term that is no longer used in polite circles, I believe. But the two alternative ways of looking at things are alive and well, I also believe.

 

[anorlunda]

I thought that the modern interpretation is that the photon is only regarded as having presence when it is interacting with a charge.

What happens when light from a star hits the surface of a neutron star?

 

[sophiecentaur]

What happens when light from a star hits the surface of a neutron star?

If GR gets involved, whatever happens, will happen very slooooowwwwwllllyyyy.
But let's deal with the simple model first. I don't know about the charge situation in a neutron star. The electric Energy levels are swamped by other forces, I imagine. And, on the way to that neutron star, we can treat it as a wave, I think.

 

[mfb]

The surface of neutron stars is made out of regular atoms.

 

[sophiecentaur]

The surface of neutron stars is made out of regular atoms.

A tad distorted, though, I would imagine. How 'thick' would its atmosphere be?

 

[anorlunda]

The surface of neutron stars is made out of regular atoms.

I love PF because I learn something every day. I would not have suspected that.

I should have said a sample of neutronium instead of a neutron star. It is hard to imagine anything as dense as neutronium being transparent.

But perhaps @mfb can answer the question more directly with particle physics. Do single photons ever interact with neutral particles?

 

[mfb]

A tad distorted, though, I would imagine. How 'thick' would its atmosphere be?

Micrometers.
A pressure similar to the core of Earth is reached at something like ten micrometers below the surface, and pressure exceeds the pressure in Jupiter's core within less than a millimeter. You have electrons and protons (maybe replaced by a quark-gluon plasma in the core) everywhere in a neutron star - their relative density just goes down towards the core. Wikipedia has a sketch

Neutrons have a magnetic moment, they do interact with photons, although the interaction is weak at low energies. At high energies, you "see" the individual quarks, and photons interact a lot with neutrons.

 

[sasan]

Dear People,

This is the bottom line:

Electromagnetic (Maxwell) waves have NOTHING to do with wave function. The only thing they have in common is the word "wave".

I hope we are all in agreement with this. Are we?

 

[sophiecentaur]

Dear People,

This is the bottom line:

Electromagnetic (Maxwell) waves have NOTHING to do with wave function. The only thing they have in common is the word "wave".

I hope we are all in agreement with this. Are we?

I would say that the common Mathematics gives them quite a lot in common. People who feel the need for what things 'really' are, would want to make more of the distinction between them.

 

[sasan]

But even reality is not real and relative more than it is relevant.

 

[B Zannelli]

No one here has come close to answering the original question. In Quantum Field theory, the photon field is described by the Proca equation and it has magnetic and electric terms in its the four vector potential , so the EM field and the probability amplitude ARE directly related. The photon probably amplitude field is the quantum version of the classical EM field