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Revision as of 18:57, 21 July 2020 by imported>Mark Widmer (Added relation to period. Clarified where discussion is specific to wave phenomena.)
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Frequency is a property of an oscillation, vibration, or other regularly-repeating (cyclic) phenomenon. The frequency of such a phenomenon is the number of repetitions (cycles) in a unit of time. In the SI system of units, frequency is measured in Hertz (Hz), the number of repetitions in one second.

Frequency ( f ) is the reciprocal of the period ( T ), which is the time interval over which the phenomenon repeats:

For a wave propagating through space, frequency ( f ) is inversely proportional to wavelength ( λ ), which is a length measurement:

, where c is the speed of propagation of the wave. For electromagnetic radiation in a vacuum, c = 299 792 458 m/s, the speed of light.

In electromagnetic radiation, the energy of the vibration is proportional to the frequency:

, where h = 6.626 x 10-34 J•s (Planck's constant)