Hertz (unit)
| Hertz | |
|---|---|
| Unit system | SI derived unit |
| Unit of | Frequency |
| Symbol | ㎐ |
| Named after | Heinrich Hertz |
| In SI base units | s−1 |
The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz (103 Hz, symbol kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), and terahertz (1012 Hz, THz).
Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the speeds at which computers and other electronics are driven.
The hertz is equivalent to cycles per second, i.e., "1/second" or . The International Committee for Weights and Measures defined the second as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom" and then adds the obvious conclusion: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9 192 631 770 hertz, ν(hfs Cs) = 9 192 631 770 Hz."
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