quanta

physics A packet of radiation possessing energy equal to h·f joules, where h is the Planck constant and f the frequency of the radiation, = (h·f160.2177~) × 10²¹ eV. For light, sometimes also photon.

sing. quantum

In physics, discrete bundles in which radiation and other forms of energy occur. For example, in the Bohr atom, light is sent out in quanta called photons. (See quantum mechanics.)