Wavelength: Difference between revisions
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imported>Paul Wormer No edit summary |
imported>Milton Beychok m (Copy edits and spelling typo. Also deleted colons which showed up at front of math expressions. Also "frequency in megahertz (Mhz) divided by 300" ==> "300 divided by the frequency in megahertz (Mhz)") |
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'''Wavelength''' is a property of an oscillation, [[vibration]], or other regularly-repeating phenomenon. The wavelength of such a phenomenon is the reciprocal of an individual repetition of the repeating event. In the [[SI]] system of units, frequency is measured in [[Hertz]] ('''Hz'''), the number of repetitions in one [[second]]. | '''Wavelength''' is a property of an [[oscillation]], [[vibration]], or other regularly-repeating (cyclic) phenomenon. The wavelength of such a phenomenon is the reciprocal of an individual repetition of the repeating event. In the [[SI]] system of units, [[frequency]] is measured in [[Hertz]] ('''Hz'''), the number of repetitions (cycles) in one [[second]]. | ||
Frequency is inversely proportional to | Frequency ( '''''f''''' ) is inversely proportional to wavelength ( '''''λ''''' ), which is a length measurement: | ||
<center> | <center><math>\lambda = \frac{c}{f} \,\!</math></center> | ||
For [[electromagnetic wave]]s propagating in vacuum c = 299,792,458 m/s (the [[speed of light]]). Rounding to convenient values for [[radio]] waves, frequency in megahertz (Mhz) | For [[electromagnetic wave]]s propagating in a vacuum, '''''c''''' = 299,792,458 m/s = 300 Mm/s (the [[speed of light]]). Rounding to convenient values for [[radio]] waves, 300 divided by the frequency in megahertz (Mhz) gives the wavelength in [[meter]]s: | ||
<center> | <center><math>\lambda = \frac{300}{f} \,\!</math></center> | ||
Three systems of designating ranges of frequencies and wavelengths are in common use: | Three systems of designating ranges of frequencies and wavelengths are in common use: | ||
*[[ITU frequency bands]], most commonly for terrestrial communications | *[[ITU frequency bands]], most commonly for terrestrial communications | ||
*[[IEEE frequency bands]], most | *[[IEEE frequency bands]], most commonly for satellite communications and civilian [[radar]] | ||
*[[EU-NATO-US frequency bands]], most commonly for military electronics | *[[EU-NATO-US frequency bands]], most commonly for military electronics | ||
Revision as of 14:37, 8 March 2010
Wavelength is a property of an oscillation, vibration, or other regularly-repeating (cyclic) phenomenon. The wavelength of such a phenomenon is the reciprocal of an individual repetition of the repeating event. In the SI system of units, frequency is measured in Hertz (Hz), the number of repetitions (cycles) in one second.
Frequency ( f ) is inversely proportional to wavelength ( λ ), which is a length measurement:
For electromagnetic waves propagating in a vacuum, c = 299,792,458 m/s = 300 Mm/s (the speed of light). Rounding to convenient values for radio waves, 300 divided by the frequency in megahertz (Mhz) gives the wavelength in meters:
Three systems of designating ranges of frequencies and wavelengths are in common use:
- ITU frequency bands, most commonly for terrestrial communications
- IEEE frequency bands, most commonly for satellite communications and civilian radar
- EU-NATO-US frequency bands, most commonly for military electronics