photon
photon
Particle of zero charge, zero rest mass, spin quantum number 1, energy <em>h</em><em>ν</em> and momentum <em>h</em><em>ν</em>/<em>c</em> (<em>h</em> is the Planck constant, <em>ν</em> the frequency of radiation and <em>c</em> the speed of light), carrier of electromagnetic force.