- In the field of optics, light is explained in terms of waves (wavelength, frequency and energy) but this description doesn’t always fit the evidence. It became clear during the 20th century that light sometimes exhibits wave-like behaviour, at others both waves and particles, or just particles.
- Contemporary physics considers that electromagnetic fields propagate through space configured as bundles of energy. These are bundles of photons.
- Photons are the force carriers of radiant energy (electromagnetic radiation).
- A photon is a type of elementary particle and represents a quantum of light (eg. visible light). Another way of putting this is that a photon is the smallest quantity (quantum, plural quanta) into which light can be divided.