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]

quantum

/quan·tum/ (kwon´tum) pl. quan´ta   [L.] a unit of measure under the quantum theory (q.v.).

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]

quantum (kwon´təm),

n a discrete unit of electromagnetic energy or of a roentgen. A quantity becomes quantized when its magnitude is restricted to a discrete set of values as opposed to a continuous set of values.
quantum theory,

quantum

pl. quanta [L.] an elemental unit of energy; the amount emitted or absorbed at each step when energy is emitted or absorbed by atoms or molecules.

quantum theory
radiation and absorption of energy occur in quantities (quanta) which vary in size with the frequency of the radiation.