1) Electromagnetic energy units 2) Electromagnetic particles 3) Gamma rays, essentially 4) Light intensity units 5) Light quanta 6) Particles in physics 7) Radiation particles Found on https://www.crosswordclues.com/clue/photons
Discrete concentrations of energy, apparently massless elementary particles, that move at the speed of light. They are the unit or quantum of electromagnetic radiation. Photons are emitted when electrons move from one energy state to another. ... (12 Dec 1998) ... Found on http://www.encyclo.co.uk/local/20973
Massless packet of energy, which behaves like both a wave and a particle. In the duality of mass/energy this is considered a “particle� of radiation.Einstein`s generalization of the concept of the quantum introduced by Max Planck. See also: Eddington Limit, Stimulated Emission, Wave Particle Duality. Found on https://www.encyclo.co.uk/local/20687