# Formula Wave in Vacuum Phase velocity    Frequency    Wavelength

## Phase velocity

Unit
Phase velocity is the speed of propagation of the same phase of a (monochromatic) wave.

In the case of electromagnetic waves, the phase velocity is the speed of light: $$c = \lambda \, f$$, with the value $$c = 299 \, 792 \, 458 \, \frac{\mathrm m}{\mathrm s}$$.

## Frequency

Unit
Frequency of the wave. Indicates how often the wave (e.g. light wave) oscillates per second.

## Wavelength

Unit
Wavelength is the smallest distance between two points of the same phase. For example, the distance between two wave crests.