What is Photon?
[[File:Lasers.jpeg|right|thumb|200px|A [[laser]] emits photons.]] '''Photons''' (from [[Greek language|Greek]] φως, meaning ''light''), in many [[atom]]ic [[model]]s in [[physics]], are [[particle]]s which [[wikt:transmit|transmit]] [[light]]. In other words, light is carried over [[Space (physics)|space]] by photons. Photon is an elementary particle that is its own [[antiparticle]]. In [[quantum mechanics]] each photon has a characteristic quantum of energy that depends on frequency: A photon associated with light at a higher frequency will have more energy (and be associated with light at a shorter wavelength). Photons have a [[rest mass]] of 0 (zero). However, [[Einstein]]'s [[theory of relativity]] says that they do have a certain amount of [[momentum]]. Before the photon got its name, Einstein revived the proposal that light is separate pieces of energy (particles). These particles came to be known as photons. A photon is usually given the [[symbol]] γ ([[gamma]]). == Properties == Photons are [[elementary particle|fundamental particles]]. Although they can be created and destroyed, their lifetime is infinite. In a [[vacuum]], all photons move at the [[speed of light]], '''c''', which is equal to 299,792,458 meters (approximately 300,000 kilometers) per second. A photon has a given frequency, which determines its color. Radio technology makes great use of frequency. Beyond the visible range, frequency is less discussed, for example it is little used in distinguishing between X-Ray photons and [[infrared]]. Frequency is equivalent to the quantum energy of the photon, as related by the [[Planck constant]] equation, :<math>E=hf</math>, where <math>E</math> is the photon's energy, <math>h</math> is the Planck constant, and <math>f</math> is the frequency of the light associated with the photon. This frequency, <math>f</math>, is typically measured in cycles per second, or equivalently, in [[Hertz|Hz]]. The quantum energy of different photons is often used in [[camera]]s, and other machines that use vi