What is the definition of photon?

Answer 1

Photons are the carriers of the electromagnetic force. Photons always come in "wavelengths." These wavelengths differ from gamma rays (wavelength 10-12 meters) to ELF (extremely low frequency) radio waves (wavelength 100000 kilometers). Visible light ranges from 390 to 750 nm (nanometers, or 10-9 meters).

Photons are also the reason positive and negatively charged particles attract, as gluons are the reason different color charges attract. These attractions are caused by the exchange, or swapping, of the gluons or photons, classified as "gauge bosons", between two particles that interact via any force. Gauge bosons, in definition, are the carriers of forces. Other gauge bosons are, as mentioned earlier, the gluon (the carrier of the strong force, or color charge), the W and Z bosons (they both are carriers of the weak force, but the Z is neutral, and the W can be charged), and the hypothetical "graviton", or the carrier of gravity.

The "wave-particle" theory is a hard concept to understand. I've heard from Steven Pollock, on a CD I bought, an excellent explanation. He says," All forces have a "field." When you "jiggle" this field, it creates a ripple, like a rock thrown in a pond does. This ripple, if in the electromagnetic field, is the photon."

Photons also carry different amounts of "eV", or "electron volts", like other particles. Mass of particles is also measured in eV. If a photon is carrying, say, 1.022 MeV (mega electron volt), it could, at any given time, turn into a positron and an electron. This matter-antimatter pair annihilates, and releases a photon carrying the same amount of energy, 1.022 MeV, or maybe a series of particles with 1.022 MeV/c2 (from E=mc2) worth of mass. The mass of each of these particles (the positron and electron) has to be 5.11 MeV/c2, or half of 1.022 MeV. The mass of the proton is .938 GeV (giga electron volt)/c2. So when a proton and an antiproton collide and annihilate, they release a photon with 1.876 GeV, a series of particles with 1.876 GeV/c2 worth of mass, or a combination of the two.
A photon is a particle of electromagnetic radiation, for example a gamma ray, x-ray, light, etc.
A quantum of electromagnetic radiation; an elementary particle that is its own antiparticle

Answer 2

A photon is a fundamental particle that carries electromagnetic radiation, such as light. It has no mass, no electric charge, and travels at the speed of light. Photons exhibit both wave-like and particle-like properties, depending on the context in which they are studied.