Frequency
The number of complete wave cycles or vibrational repetitions occurring per unit time.
Governing formula
f = 1 / T = v / λ
SI unit
Hz (s⁻¹)
In depth
Frequency quantifies vibrational speed. In acoustics, frequency determines perceived musical pitch. In electromagnetic waves, higher frequency corresponds to higher photon energy (E = hf).
Examples in the real world
Audible human sound range spanning 20 Hz to 20,000 Hz, or concert pitch middle A vibrating at 440 Hz.