Wave-particle duality and my non-physicist friend

In summary: I appreciate the responses.In summary, my friend said that physicists have not decided whether light is a wave or a particle, but that quantum physics tells us that photons are quanta of electromagnetic waves. Phonons are similar to photons, in that they are quanta of sound, and use QFT methods to understand them.
  • #1
Guineafowl
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Hi, I'm a vet with an amateur interest in physics. In discussion with a friend about the usefulness of physics he stated that physicists had not even decided whether light was a wave or a particle. I said the following:

'The question of whether light is a wave or particle is not one which really troubles modern physicists. A photon is not something we can describe in terms of things we humans can see with our eyes. If you do an experminent to see if light is a wave, it is; if you do the same for particles, it is too. Quantum physics tells us that photons are quanta of electromagnetic waves, so if you were to twist my arm I'd say it is a particle which has emergent wavelike properties. Photons are described by wavefunctions and governed by quantum amplitudes; these are complex numbers and as such have a magnitude and also a phase. This phase rotates as time goes on and gives rise to an illusion of wavelike behaviour.'

Was I taking crap?
 
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  • #2
A photon is a particle only in the quantum field theoretical sense. This is not what you would tend to call a particle in classical mechanics. A photon is also not a wave.

However, what we call particles in QFT are objects that have some properties reminiscent of waves and some that are reminiscent of classical particles.

My short answer would have been that it is neither, but it has some properties that we typically ascribe to particles and waves.
 
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  • #3
You can also see our FAQ:
https://www.physicsforums.com/threads/is-light-a-wave-or-a-particle.511178/

However if you want to learn the technical detail and have an understanding way beyond popularisations a wonderful book has recently been released:
https://www.amazon.com/dp/019969933X/?tag=pfamazon01-20

I am studying it right now and my knowledge of QFT has benefited a lot.

Its big advantage is that your background in ordinary QM doesn't have to be at an advanced level - Susskinds book is good enough:
https://www.amazon.com/dp/0465036678/?tag=pfamazon01-20

Thanks
Bill
 
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  • #4
Orodruin said:
A photon is a particle only in the quantum field theoretical sense.

What about the concept of phonon in the context of condensed matter ? Is there similarity between these two concepts that can be use to better understand the concept of photon defined in a given theoretical framework ?

Patrick
 
  • #5
Guineafowl, to add to what has already been said (with some repetition), the best SIMPLE way to express it is to simply say that light is a quantum object (as are electrons, for example, and this means it is not a particle and not a wave, it is it's own thing which is neither but has some of the characteristics of both)
 
  • #6
microsansfil said:
What about the concept of phonon in the context of condensed matter ? Is there similarity between these two concepts that can be use to better understand the concept of photon defined in a given theoretical framework ?

Sure. They both use similar QFT methods. Its not any easier however.

Thanks
Bill
 
  • #7
Guineafowl said:
Hi, I'm a vet with an amateur interest in physics. In discussion with a friend about the usefulness of physics he stated that physicists had not even decided whether light was a wave or a particle.
Is your friend also a veterinarian? Because this is like saying that vets haven't even decided whether a frog is a fish or a reptile. It has properties of both, and yet it's neither.
 
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  • #8
TeethWhitener said:
Is your friend also a veterinarian? Because this is like saying that vets haven't even decided whether a frog is a fish or a reptile. It has properties of both, and yet it's neither.
Thanks for all your replies. My friend is actually an acquaintance, and is really a Jehovah's witness who came to the door, but my original thread with this information got deleted.
 

1. What is wave-particle duality?

Wave-particle duality is the concept in quantum mechanics that states that particles can exhibit both wave-like and particle-like behavior. This means that they can act as both a discrete particle and a continuous wave at the same time.

2. How does wave-particle duality relate to light?

Wave-particle duality was first observed in experiments with light, where it was found that light can exhibit both wave-like and particle-like properties. This led to the development of the photon theory of light, which describes light as both a particle and a wave.

3. Can you give an example of an experiment that demonstrates wave-particle duality?

One famous experiment that demonstrates wave-particle duality is the double-slit experiment. In this experiment, a beam of light is shone through two parallel slits, creating an interference pattern on a screen behind the slits. This pattern can only be explained by light behaving as both a wave and a particle.

4. How does wave-particle duality challenge our understanding of the world?

Wave-particle duality challenges our classical understanding of physics, where particles and waves were thought to be distinct and separate. It forces us to rethink our concepts of reality and how the universe works at a fundamental level.

5. Can you explain wave-particle duality in simple terms?

Wave-particle duality can be understood as the idea that particles can behave like waves and waves can behave like particles. Just like how light can act as both a particle (photon) and a wave (electromagnetic radiation), other particles such as electrons and protons can also exhibit this duality.

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