Hertz

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The hertz (symbol: Hz) is the SI unit of frequency. Its base unit is s^-1 (also called inverse seconds, or 1/s). In English, hertz is used as both singular and plural.

One hertz simply means "one cycle per second"; 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. The frequency of aperiodic events, such as radioactive decay, are expressed in becquerels.

History

The hertz is named after the German physicist Heinrich Rudolf Hertz, who made important scientific contributions to electromagnetism. The name was established by the IEC in 1930 [1]. It was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples, primarily kilocycles (kc) and megacycles (Mc). The term cycles per second was largely replaced by hertz by the 1970's.

SI multiples

Multiple	Name	Symbol		Multiple	Name	Symbol
100	hertz	Hz
101	decahertz	daHz		10–1	decihertz	dHz
102	hectohertz	hHz		10–2	centihertz	cHz
103	kilohertz	kHz		10–3	millihertz	mHz
106	megahertz	MHz		10–6	microhertz	µHz
109	gigahertz	GHz		10–9	nanohertz	nHz
1012	terahertz	THz		10–12	picohertz	pHz
1015	petahertz	PHz		10–15	femtohertz	fHz
1018	exahertz	EHz		10–18	attohertz	aHz
1021	zettahertz	ZHz		10–21	zeptohertz	zHz
1024	yottahertz	YHz		10–24	yoctohertz	yHz

Applications

Sound is a travelling wave which is an oscillation of pressure. Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be scientifically measured in hertz. Although the human ear is able to perceive frequencies ranging from 16 Hz to 20,000 Hz, the average human can hear sounds between 20 Hz and 16,000 Hz.

See also

• Frequency converter
• Wavelength
• Orders of magnitude (frequency)

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