quantum

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quantum

 [kwon´tum] (L.)
an elemental unit of energy; the amount emitted or absorbed at each step when energy is emitted or absorbed by atoms or molecules.

quan·tum

, pl.

quan·ta

(kwahn'tŭm, -tă),
1. A unit of radiant energy (Q) varying according to the frequency (ν) of the radiation.
2. A certain definite amount.
[L. how much]

quan·tum

, pl. quanta (kwahn'tŭm, -tǎ)
1. A unit of radiant energy (ε) varying according to the frequency (ν) of the radiation.
2. A certain definite amount.
[L. how much]

quantum

  1. a quantity or amount.
  2. the minimum quantity in which a neurotransmitter is secreted.
  3. a unit of light.

photon 

The basic unit of radiant energy defined by the equation
E = hν
where h is Planck's constant (6.62 ✕ 10−34 joule ✕ second), ν the frequency of the light and E the energy difference carried away by the emission of a single photon of light. The term photon usually refers to visible light whereas the term quantum refers to other electromagnetic radiations. See quantum theory; wave theory; troland.

quan·tum

, pl. quanta (kwahn'tŭm, -tǎ)
Unit of radiant energy (Q) varying by frequency (ν) of radiation.
[L. how much]