Other forms: photons
In physics, a photon is a tiny bundle of matter that transmits light. You can also think of photons as little bits of electromagnetic energy.
Light is made up of small amounts of energy which are known as photons. You can tell how much radiation is being emitted by the number of photons — think of a dimmer on a light switch, with the brighter light emitting more photons. Albert Einstein was instrumental in developing the photon theory of light, although he used the term "the light quantum," rather than photon, which was first used in this sense around 1926.