Wavelength: Difference between revisions
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)") |
imported>Mark Widmer (Added typical wavelength values for: FM & AM radio, visible light.) |
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'''Wavelength''' is a property of | '''Wavelength''' is a property of a phenomenon that regularly repeats in space (as opposed to time). The wavelength of such a phenomenon is the distance over which the phenomenon repeats. In the [[SI]] system of units, [[wavelength]] is measured in metres ('''m'''). | ||
Wavelength ( '''''λ''''' ) can be determined from the wave speed ( '''''c''''' ) and [[frequency]] ( '''''f''''' ): | |||
<center><math>\lambda = \frac{c}{f} \,\!</math></center> | <center><math>\lambda = \frac{c}{f} \,\!</math></center> | ||
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<center><math>\lambda = \frac{300}{f} \,\!</math></center> | <center><math>\lambda = \frac{300}{f} \,\!</math></center> | ||
Three systems of designating ranges of frequencies and wavelengths are in common use: | Thus FM radio waves, with a frequency of roughly 100 MHz, have a wavelength of around 3 m, while the wavelength of AM radio waves (roughly 1000 kHz or 1 MHz frequency) have much longer wavelengths, around 300 m. | ||
Three systems of designating ranges of electromagnetic wave 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 commonly for satellite communications and civilian [[radar]] | *[[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 | ||
For visible light, wavelengths are several hundred nanometres, or several tenths of a micrometre. | |||
Latest revision as of 19:41, 21 July 2020
Wavelength is a property of a phenomenon that regularly repeats in space (as opposed to time). The wavelength of such a phenomenon is the distance over which the phenomenon repeats. In the SI system of units, wavelength is measured in metres (m).
Wavelength ( λ ) can be determined from the wave speed ( c ) and frequency ( f ):
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:
Thus FM radio waves, with a frequency of roughly 100 MHz, have a wavelength of around 3 m, while the wavelength of AM radio waves (roughly 1000 kHz or 1 MHz frequency) have much longer wavelengths, around 300 m.
Three systems of designating ranges of electromagnetic wave 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
For visible light, wavelengths are several hundred nanometres, or several tenths of a micrometre.