Difference between revisions 1390326 and 1412088 on enwikiversity

[[File:EM Spectrum Properties edit.svg|thumb|right]]
'''Electromagnetic radiation''' comes in many different types, although the differences between them are quantitative rather than qualitative.  This teaching aid lists the different types that are generally recognised.

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* '''Ultra high frequency (UHF)''': Frequencies of 300MHz to 3GHz, hence wavelengths of 10cm to 1m.  This overlaps with the microwave region.
* '''Very high frequency (VHF)''': Frequencies of 30MHz to 300MHz, hence wavelengths of 1m to 10m.
* '''High frequency (HF)''': Frequencies of 3MHz to 30MHz, hence wavelengths of 10m to 100km.
* '''Medium frequency (MF)''': Frequencies of 300k
hHz to 3MHz, hence wavelengths of 100m to 1km.  These are also called '''hectometric waves''' (hectometre = 100m).
* '''Low frequency (LF)''': Frequencies of 30khHz to 300kHz, hence wavelengths of 1km to 10km.
* '''Very low frequency (VLF)''': Frequencies of 10khHz to 30kHz, hence wavelengths of 10km to 30km.
* '''Ultra low frequency (ULF)''': Frequencies of 300Hz to 10khHz, hence wavelengths of 30km to 1000km; these are mainly used for long-distance underwater transmission.
* '''Extremely low frequency (ELF)''': The lowest frequencies (below 300 Hz; wavelength > 1000km).

Sometimes a division by wavelength is used:

* '''Short wave (SW)''': Wavelengths of 10-200m hence frequencies of 1.5-33MHz; there are several sub-bands.
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There is no lower boundary to the wavelength hence no upper bound to frequency or photon energy.  In October 2011, photons with energies exceeding 100 billion eV, i.e. over a million times the lower limit, were detected from the Crab pulsar.[http://www.sciencedaily.com/releases/2011/10/111006141358.htm]

== See also ==
* [[Electromagnetic fields and waves]]

[[Category:Resources last modified in April 2012]]
[[Category:Physics]]