Quantum Waves for Different Particles
Most recent answer: 05/20/2012
Q:
If photons are waves in the electro-magnetic field, which field do proton and electron waves propagate in?
Also, since wave properties apply to all matter, in which field would propagate a wave of a bullet, flying at the speed of light?
- Ilya Kiselev (age 17)
Moscow, Russia
- Ilya Kiselev (age 17)
Moscow, Russia
A:
It's not quite accurate to say that "photons are waves in the electromagnetic field". The electromagnetic field is a classical approximation to the behavior of the full quantum photon field. Under some circumstances, the difference between the full behavior and the classical approximation can be striking. For example, any quantum field with a definite number of photons, no matter how large, has expectation values of zero for the classical electric and magnetic fields.
So, although this isn't exactly helpful, I'd say that photon waves are in the photon field, electron waves are in the electron (more accurately, electron-positron) field, etc.
What about a bullet? It can't propagate at the speed of light, since it has rest mass, but we can still address your question about its wave properties. For some composite objects one can approximately write a single wave for the whole thing in. For example, that procedure sort of works for C60 buckyballs. That approximation breaks down if internal vibrations etc. of the object are significant, in which case you need extra properties to describe the object. The behavior of an atomic nucleus can typically be described as a wave in a single field, since the nucleus is typically stuck in its lowest-energy internal state. The bullet will have many, many possible internal states and thus require a more complicated description. In principle, its wave could be written in terms of waves for the electrons, protons, neutrons, etc. of which it's composed. In practice, a classical description is far more practical.
Mike W.
So, although this isn't exactly helpful, I'd say that photon waves are in the photon field, electron waves are in the electron (more accurately, electron-positron) field, etc.
What about a bullet? It can't propagate at the speed of light, since it has rest mass, but we can still address your question about its wave properties. For some composite objects one can approximately write a single wave for the whole thing in. For example, that procedure sort of works for C60 buckyballs. That approximation breaks down if internal vibrations etc. of the object are significant, in which case you need extra properties to describe the object. The behavior of an atomic nucleus can typically be described as a wave in a single field, since the nucleus is typically stuck in its lowest-energy internal state. The bullet will have many, many possible internal states and thus require a more complicated description. In principle, its wave could be written in terms of waves for the electrons, protons, neutrons, etc. of which it's composed. In practice, a classical description is far more practical.
Mike W.
(published on 05/20/2012)
Follow-Up #1: Is light made of photons?
Q:
I have a question. My understanding is that light is electromagnetic oscillations, and photons carry this information. So what I'm saying is: Is it true light is not made of photons, rather photons carry the information of light and that light, really, is the electromagnetic oscillation?
- lawrence (age 34)
England
- lawrence (age 34)
England
A:
I've moved your follow-up to another question which seemed to come even closer to yours than did
There's just one type of quantum wave involved. The information, energy, momentum, and angular momentum carried by this wave are not carried by separate physical entities.The electromagnetic fields are one of the symptoms of this quantum wave. However, classical electromagnetism is only an approximation to the full quantum behavior. That behavior includes the tendency, under typical circumstances, to transfer energy to other things in photon-sized lumps.
Mike W.
(published on 05/25/2012)