Frequency formula with wavelength, and speed

As a unit of wave frequency, a hertz is equal to one cycle per second. The hertz is used widely in the study of electromagnetic waves, and by extension the study of matter itself, because everything in the universe consists of vibrating atoms.

It's also common in electric technology, because electricity is generated by rotating turbines that create current that alternates with a fixed frequency.

If you know the frequency (​f​) and wavelength (​λ​) of a waveform, you can multiply these together to obtain the velocity of the wave:

\(v=\lambda f\)

Consequently, you can derive the frequency if you know the velocity and wavelength:

\(f=\frac{v}{λ}\)

To get frequency in hertz, the velocity must be in "units of length" per second, and the wavelength must be measured in the same "units of length." For example, if velocity is measured in m/s, the wavelength must be measured in meters.