# 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

- a quantity or amount.
- the minimum quantity in which a neurotransmitter is secreted.
- a unit of light.

## photon

The basic unit of radiant energy defined by the equationwhere

*E*=

*h*ν

*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**,

*n*See theory, quantum.

## 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.

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