# Hertz (unit)

 symbol cycles per second frequency (f, ν) 1/s

Hertz (abbreviation cycles per second) is those SI - unit for the frequency. The unit was designated after the German physicist Heinrich Rudolf Hertz. Hertz gives the number to that Oscillations per second on, more generally also the number of arbitrary itself repeating procedures per second. Hertz is limited to regularly returning procedures - normally oscillations -; for irregularly repeating procedures one leads own units (like z.B. for the Becquerel, where it concerns statistically varying radioactive decay events, for which one can indicate only an average rate).

1 cycles per second = 1 s -1 = 1/s

in the oscillation measuring technique often become the number of revolutions of a machine in Hertzindicated. One speaks then of turning frequency.

1 cycles per second = 1 U/s = 60 rpm

frequent used larger units are

• kilohertz, kHz, thousand oscillations/procedures per second
• the megahertz, MHz, one million oscillations/procedures per second
• the gigahertz, GHz, a billion oscillations/procedures per second
• the Terahertz, THz, one trillion oscillations/procedures per second
 name symbol factor name symbol factor Yotta Zetta Exa Peta Tera Giga mega Kilo of Hekto Deka Y Z E P T G M k h there 10 24 10 21 10 18 10 15 10 12 10 9 10 6 10 3 10 2 10 1 Dezi Zenti milli micro nano pico Femto Atto Zepto Yocto D C m µ n p f A z y 10 -1 10 -2 10 -3 10 -6 10 -9 10 -12 10 -15 10 -18 10 -21 10 -24

the name “Hertz” became 1960 of the CGPM (Conférence Générale of the Poids et Mesures) ofEnglish-language countries taken over and replaced the there usual name for this unit of cycles by second = cps (cycles per second). Therefore one finds in older English-language literature instead of Hertz still cps.

## examples

given is a rope, which is fastened at a side. This rope swings - with something fate - as standing wave. The length of this wave depends on 2 factors,the speed of the wave propagation, as well as the frequency, with which the rope is moved.

With a flute or a whistle now air swings. The propagation speed is here clearly higher and is for instance about 330 meters (speed of sound) per second. Herean oscillation with an audible audio frequency few centimeters up to some meters is long.

Electromagnetic waves spread with speed of light. For example there a wave has, with a frequency of a megahertz about the wavelength of 300 meters. That means, ifone for example a lamp one million time per second would switch on and off, then a viewer into 150 meters distance the lamp to see switched on whenever she is actually switched off.

With frequencies in the Gigahertz-Bereich is the wavelength (λ) many smaller, for example: Wavelength in the Mikrowellenofen approx. 12 cm, wavelength with the domestic satellite television receipt approx. 2.5 cm.

## donkey bridge

the heart of an adult strikes in dwell phases between 50 and 80 times per minute. Thus with oneFrequency of approximately 1 cycles per second.

In addition applies to the conversion the wavelength into the frequency: Yellow light of approximately 600 Nm correspond to a frequency of 500 THz, which corresponds again to an energy of 2,5 eV (electronvolts).

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