# Formula Wave in Vacuum Phase velocity Frequency Wavelength

## Phase velocity

`$$ v_{\text p} $$`Unit

`$$ \frac{\mathrm m}{\mathrm s} $$`

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

`$$ f $$`Unit

`$$ \mathrm{Hz} = \frac{ 1 }{ \mathrm{s} } $$`

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

## Wavelength

`$$ \lambda $$`Unit

`$$ \mathrm{m} $$`

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