Originally posted by DA Morgan:
dr_rocket wrote:
"Rob asked "so what proof is there that a photon is a particle and not a wave?"
I don't know if "proof""
And quite frankly there is none and never will be any. Because a photon is not a wave. And a photon is not a particle. And a photon is not some new-age mixture of the two.
A photon is a photon is a photon. All of these words like "wave" and "particle" refer to analogies in mathematic that help us describe and predict the behavior.
No physical entity changes its form to comfortably comply with our wishes.
A wave can act like a wave and like a particle. A time-independent localised electron-wave has a centre of mass just like a particle, and when observed from an inertial reference frame moving relative to the time-independent wave, the centre of mass will move like a "point-particle". What happens to a photon when it excites an electron? It disappears. This is strange behaviour for a photon is a photon is a photon; suddenly it is a "nothing". What happens is that the photon entangles with the electron wave, thus increasing its energy so that it has to morph, within a time delt(t) as determined by Heisenberg's uncertainty for energy and time, into another atomic orbital (wave).
Now the photo-electric effect: the incoming photon entangles with the electron-wave thus increasing its energy. If this energy is equal to the workfunction, the electron-wave morphs into a free electron wave that is stationary relative to the metal substrate. If the photon has more energy, the electron wave it entangles with, morphs into a free electron wave with kinetic energy relative to the metal substrate. You do not need "particles" colliding; every interaction can be described in terms of waves entangling, or waves that superpose. A photon is a wave, a wave a wave, which can change its shape and size. Only its energy is quantized NOT its locality. It has to localise in order to entangle with an atomic electron wave.
The quantum-mechanical energy of a free stationary electron wave is its mass; i.e. it has potential energy. Thus solving a wave equation (whether Schroedinger's or Dirac's) by setting the potential energy of a free electron equal to zero, is a futile calculation. You must have a potential energy term that accounts for the rest mass of the electron. The energy of an atomic electron orbital is thus less than the rest mass of the electron. The difference is the energy required to set the electron free and ionise the atom.
