Frequency

Frequency is a property of an oscillation, vibration, or other regularly-repeating phenomenon. The frequency of such a phenomenon is the number of repetitions in a unit time. In the SI system of units, frequency is measured in Hertz (Hz), the number of repetitions in one second.

The frequency of vibrations is inversely proportional to wavelength, which is a length measurement.

$\lambda ={\frac {c}{f}}\,\!$, where c is the speed of propagation of waves in the medium, or, for electromagnetic radiation, c = 299 792 458 m/s, the speed of light.

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

$E=hf\,\!$ , where h = 6.626 x 10^-34 J•s (Planck's constant)