When is a particle not a particle?

  • I can think of two instances. How about you?

I used to ask my kids,”When is a door not a door?”

When it is ajar. We used to have a car that would say, “The door is ajar” whenever someone did not close it completely.

  • Neat car!.
  • A particle is not a particle when it’s a wave; i.e. when it’s more than one non-dimensional “point of mass”.
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I suspect “ajar” is not the other instance you have in mind.

Actually, I may have misspoken; after all, Dalton’s atom is, not really an “un-cuttable”, it has parts … a lot of them.

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Though our professor for “Physics of Light and Color” said that a photon is always a wave, that treating it as a particle is a human fiction.

Your professor is an uneducated idiot and shouldn’t be teaching things which are patently false.

A photon is demonstrably a particle just much as it is demonstrably a wave.

You can demonstrate its particulate nature with the photo-electric effect, just as you can demonstrate its wave nature with interference patterns. And with a two slit experiment experiment you can show that a detector on one of the slits will eliminate the interference pattern just by measuring which of the two slits the photon particle passes through. Thus showing that the photon is only a wave when you don’t ask it to be a particle (with your measuring devices).

Given that he not only had a PhD in physics and had authored two textbooks used in numerous universities, I doubt that.

No, it behaves like a particle sometimes – but “particle” is just a human category used to describe that behavior.

Ok… I guess even educated people can teach things which are demonstrably false.

No it behaves like a wave sometimes – but “wave” is just a human category used to describe that behavior.

Wave and particle are classical concepts and the truth is neither one of these describes the photon correctly. If it is wavelike then it certainly is not a classic wave… and if it is particle then it is certainly not a classic particle.

Its wavelike nature is important in the science of optics, but its particle like behavior is more important in most other physical sciences.

A photon always behaves as a wave, just not always the same kind.

Even calling it a photon contradicts saying it is a wave. That word is for a particle. If it really were a wave then there wouldn’t be any such thing as a photon. Light has wave-like properties, but it consists of photons which are particles. AND the fact is that this photon is no different than any other particle. ALL of these PARTICLES (electron, quark, pion, proton, gluon… etc…) have the same wave-like properties.

The photon creates a wave pattern due to it’s spin. A wave is not a ‘thing’; it’s a pattern due to the motion of real things. A photon has a linear velocity of ‘c’ and a spin velocity of ‘c’ which is why c^2 shows up in lots of physics equations.

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