The frequency is given in hertz( Hz) and for larger values it is prefixed with kilohertz ( kHz), megahertz( MHz), gigahertz( GHz) and terahertz( THz). One hertz means that a complete cycle of oscillations is passed in one second. The frequency is the reciprocal value of the period duration.
The frequency applies equally to acoustic, electromagnetic and optical forms of vibration. For technical use, all frequencies have been divided into frequency ranges and frequency bands. The entire frequency range extends from extremely low vibrations, which are caused by mechanical processes and cannot be heard by humans, through the audible frequency range, the various high frequencies transmitted with electromagnetic waves, to the frequencies of light, which are in the petahertz range.