B Probability Amplitude: Understanding Photons

[Daniel Petka]

https://www.physicsforums.com/attachments/197770The path of a photon is a perfect straight line not a sine wave, right? (if the probability amplitude is zero)https://www.physicsforums.com/attachments/197771

 

[mfb]

The y-axis is the strength of the electric (or magnetic), field, not a position.

A photon does not have a path.

 

[Nugatory]

The path of a photon is a perfect straight line not a sine wave, right? (if the probability amplitude is zero)

The attached image is a graph showing the strength of the electric and magnetic fields associated with a classical electromagnetic wave at different places at the same time. It has nothing to do with photons (which, as mfb says, don't have a path).

 

[zonde]

A photon does not have a path.

This is interpretation dependent statement.

 

[weirdoguy]

How can this be interpretation dependent statement if there is no position operator for photons (which AFAIK is not interpretation dependent)?

 

[zonde]

If a model would make prediction that leads to discontinuous path for a photon you could say that photon does not have a path. If a model is silent on the matter you can't draw any conclusions from that.

 

[Daniel Petka]

If a photon doesn't have any path, how can it then interact with let's say only electrons in front of him? Common sense tells me that light must have a path.

 

[bhobba]

If a photon doesn't have any path, how can it then interact with let's say only electrons in front of him? Common sense tells me that light must have a path.

Why do you think a photon has the property of something in front of it?

As has been said many times before be very careful of ascribing properties to quantum objects independent of actual observation.

QM and commonsense are not necessarily the best of friends.

Thanks
Bill

 

[Nugatory]

Common sense tells me that light must have a path.

Light has a path, but that doesn't mean a photon does. A beam of light is not a stream of photons flowing by the way a river is a stream of water molecules flowing by.

Our common sense comes from a lifetime of experience with macroscopic objects obeying the laws of classical physics, so doesn't work especially well for quantum objects. Your common sense was already leading you astray when it tempted you to think about how a photon might interact with an electron "in front" of it; what does "in front" or "behind" mean for something that has no position?

 

[Daniel Petka]

Ok... photons are strange [emoji23]

 

[Nugatory]

Ok... photons are strange [emoji23]

They are indeed... much of the problem comes from the word "particle", which as used in quantum physics doesn't mean at all what you'd expect from the common English-language meaning of the word. Photons are especially complicated because they have no rest mass, so cannot be treated using "ordinary" non-relativistic quantum mechanics, the stuff you study in your first few undergraduate years.

The links in the first two posts of this thread are pretty good but maybe a bit more than you're up for.

 

[Daniel Petka]

OK but please don't tell me that photons don't have a 3 dimensional orientation... cause then my brain's going to explodes

 

[Jilang]

OK but please don't tell me that photons don't have a 3 dimensional orientation.

Are you referring to the polarisation here?

 

[Mentz114]

OK but please don't tell me that photons don't have a 3 dimensional orientation... cause then my brain's going to explodes

I think the polarization angle lies in the plane orthogonal to the momentum. Which is only one degree of freedom.