Question

which unit is used for frequency

Answer 1

Hertz is the unit used for frequency.

Answer 2

hertz

Wavelength is also measured in metres (m) - it is a length after all. The frequency, f, of a wave is the number of waves passing a point in a certain time. We normally use a time of one second, so this gives frequency the unit hertz (Hz), since one hertz is equal to one wave per second.