What is a proton

Under the photon theory of light, a photon is a discrete bundle (or quantum) of electromagnetic (or light) energy. Photons are always in motion and, in a vacuum, have a constant speed of light to all observers, at the vacuum speed of light (more commonly just called the speed of light) of c = 2.998 x 108 m/s.

Basic Properties of PhotonsAccording to the photon theory of light, photons . . .

• move at a constant velocity, c = 2.9979 x 108 m/s (i.e. "the speed of light"), in free space
• have zero mass and rest energy.
• carry energy and momentum, which are also related to the frequency nu and wavelength
• lamdba of the electromagnetic wave by E = h nu and p = h / lambda.
• can be destroyed/created when radiation is absorbed/emitted.
• can have particle-like interactions

http://physics.about.com/od/lightoptics/f/photon.htm

- Valentia