Editing Electromagnetic spectrum (section)

== Regions <span class="anchor" id="Bands"></span> ==
[[File:Electromagnetic-Spectrum.svg|thumb|300px|The '''electromagnetic spectrum''']]
[[File:Electromagnetic spectrum, NASA illustration.jpg|thumb|330px|A visualization of the electromagnetic spectrum.]]

The types of electromagnetic radiation are broadly classified into the following classes (regions, bands or types):<ref name="em-spectrum"/>
# Gamma radiation
# X-ray radiation
# Ultraviolet radiation
# Visible light (light that humans can see)
# Infrared radiation
# Microwave radiation
# Radio waves
This classification goes in the increasing order of wavelength, which is characteristic of the type of radiation.<ref name="em-spectrum"/>

There are no precisely defined boundaries between the bands of the electromagnetic spectrum; rather they fade into each other like the bands in a [[rainbow]]. Radiation of each frequency and wavelength (or in each band) has a mix of properties of the two regions of the spectrum that bound it. For example, red light resembles infrared radiation, in that it can excite and add energy to some [[chemical bond]]s and indeed must do so to power the chemical mechanisms responsible for [[photosynthesis]] and the working of the [[visual system]].

In atomic and nuclear physics, the distinction between X-rays and gamma rays is based on sources: the photons generated from [[nuclear decay]] or other nuclear and subnuclear/particle process are termed gamma rays, whereas X-rays are generated by [[electron]]ic transitions involving energetically deep inner atomic electrons.<ref>
{{cite book
 |author1=Feynman, Richard |author2=Leighton, Robert |author3=Sands, Matthew
 |title = The Feynman Lectures on Physics, Vol.1
 |url=https://www.feynmanlectures.caltech.edu/I_toc.html |publisher = Addison-Wesley
 |year = 1963
 |location = US
 |pages = [https://www.feynmanlectures.caltech.edu/I_02.html#Ch2-S2-p10 2–5]
 |isbn = 978-0-201-02116-5}}</ref><ref>{{cite book
 |author1=L'Annunziata, Michael  |author2=Baradei, Mohammad
 |title = Handbook of Radioactivity Analysis
 |publisher = Academic Press
 |year = 2003
 |page = 58
 |url = https://books.google.com/books?id=b519e10OPT0C&q=gamma+x-ray&pg=PA58
 |isbn = 978-0-12-436603-9}}</ref> Electronic transitions in [[muonic atom]]s transitions are also said to produce X-rays.<ref>[http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-0335.pdf Corrections to muonic X-rays and a possible proton halo] {{Webarchive|url=https://web.archive.org/web/20170313134112/http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-0335.pdf |date=2017-03-13 }} slac-pub-0335 (1967)</ref> In astrophysics, energies below 100keV are called X-rays and higher energies are gamma rays.<ref name=Grupen-2005>{{cite book
 |author1=Grupen, Claus |author2=Cowan, G. |author3=Eidelman, S. D. |author4=Stroh, T. |title = Astroparticle Physics
 |url=https://archive.org/details/astroparticlephy00grup |url-access=limited |publisher = Springer
 |year = 2005
 |page = [https://archive.org/details/astroparticlephy00grup/page/n123 109]
 |isbn = 978-3-540-25312-9
}}</ref>

The region of the spectrum where electromagnetic radiation is observed may differ from the region it was emitted in due to relative velocity of the source and observer, (the [[Doppler shift]]), relative gravitational potential ([[gravitational redshift]]), or expansion of the universe ([[cosmological redshift]]).<ref name=Grupen-2005/>{{rp|543}} For example, the [[cosmic microwave background]], relic [[blackbody radiation]]  from the era of [[recombination (cosmology)|recombination]], started out at energies around 1eV, but as has undergone enough cosmological [[red shift]] to put it into the microwave region of the spectrum for observers on Earth.<ref>{{Cite journal |last1=Samtleben |first1=Dorothea |last2=Staggs |first2=Suzanne |last3=Winstein |first3=Bruce |date=2007-11-01 |title=The Cosmic Microwave Background for Pedestrians: A Review for Particle and Nuclear Physicists |url=https://www.annualreviews.org/doi/10.1146/annurev.nucl.54.070103.181232 |journal=Annual Review of Nuclear and Particle Science |language=en |volume=57 |issue=1 |pages=245–283 |doi=10.1146/annurev.nucl.54.070103.181232 |arxiv=0803.0834 |bibcode=2007ARNPS..57..245S |issn=0163-8998}}</ref>

{| class="wikitable outercollapse" style="float:center; text-align:center; margin:1em 1em 1em 1em; line-height:1;"
|-
! colspan=3 | Class<!---col 1,2,3--->
! style="padding:0;font-size:1px;" | <!---col 4 (empty)--->
! [[Wavelength|Wave-<br />length]]<br /><math> \lambda </math><!---col 5--->
! [[Frequency|Freq-<br />uency]]<br /><math>f</math><!---col 6--->
! [[Photon energy|Energy per<br />photon]]<br /><math>E</math><!---col 7--->
|-
| rowspan="5" | [[Ionizing radiation|Ionizing<br />radiation]]<!---col 1--->
| rowspan="2" | γ<!---col 2--->
| rowspan="2" | [[Gamma ray]]s<!---col 3--->
| rowspan="35" style="background:#fff; padding:0; font-size:1px;" | <!---col 4 (empty)--->
| style="text-align:right;" | 10 [[Picometre|pm]]<!---col 5--->
| style="text-align:right;" | 30 [[Exahertz|EHz]]<!---col 6--->
| style="text-align:right;" | 124 [[keV]]<!---col 7--->
|-
| rowspan="2" style="text-align:right;" | 100 pm<!---col 5--->
| rowspan="2" style="text-align:right;" | 3 EHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 12.4 keV<!---col 7--->
|-
| HX<!---col 2--->
| Hard [[X-ray]]s<!---col 3--->
|-
| SX<!---col 2--->
| Soft X-rays<!---col 3--->
| style="text-align:right;" | 10&nbsp;nm<!---col 5--->
| style="text-align:right;" | 30 PHz<!---col 6--->
| style="text-align:right;" | 124 [[Electronvolt|eV]]<!---col 7--->
|-
| EUV<!---col 2--->
| [[Extreme ultraviolet|Extreme<br />ultraviolet]]<!---col 3--->
| style="text-align:right;" | 121&nbsp;nm<!---col 5--->
| style="text-align:right;" | 3 PHz<!---col 6--->
| style="text-align:right;" | 10.2 eV<!---col 7--->
|-
| <!---col 1--->
| NUV<!---col 2--->
| [[Near ultraviolet]]<br /><!---col 3--->
| style="text-align:right;" | 400&nbsp;nm
| style="text-align:right;" | 750 THz
| style="text-align:right;" | 3.1 eV<!---col 7--->
|-
| style="background:linear-gradient(to bottom,#f6f 0%,#0ff 30%,#ff0 80%,#f66 100%);" | <!---col 1--->
|
|[[Visible spectrum]]
| style="text-align:right;" | 700&nbsp;nm
| style="text-align:right;" | 480 THz
| style="text-align:right;" | 1.77 eV<!---col 7--->
|-
| rowspan="6" |[[Infrared]]<!--col 1-->
| rowspan="2" | NIR<!---col 2--->
| rowspan="2" | Near [[infrared]]<!---col 3--->
| style="text-align:right;" | 1 [[Micrometre|μm]]<!---col 5--->
| style="text-align:right;" | 300 [[Terahertz (unit)|THz]]<!---col 6--->
| style="text-align:right;" | 1.24 eV<!---col 7--->
|-
| rowspan="2" style="text-align:right;" | 10  μm<!---col 5--->
| rowspan="2" style="text-align:right;" | 30  THz<!---col 6--->
| rowspan="2" style="text-align:right;" | 124 [[meV]]<!---col 7--->
|-
| rowspan="2" | MIR<!---col 2--->
| rowspan="2" | Mid infrared<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 100 μm<!---col 5--->
| rowspan="2" style="text-align:right;" | 3 THz<!---col 6--->
| rowspan="2" style="text-align:right;" | 12.4 meV<!---col 7--->
|-
| rowspan="2" | FIR<!---col 2--->
| rowspan="2" | [[Far infrared]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1 [[Millimetre|mm]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 300  [[Gigahertz|GHz]]<!---col 6--->
| rowspan="2" style="text-align:right;" | 1.24 meV<!---col 7--->
|-
| rowspan="6" | [[Microwave|Micro-<br />waves<ref name="ITU-WRC-15"/>]]<!---col 1--->
| rowspan="2" | EHF<!---col 2--->
| rowspan="2" | [[Extremely high frequency|Extremely high<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1  [[Centimetre|cm]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 30&nbsp;GHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 124 [[μeV]]<!---col 7--->
|-
| rowspan="2" | SHF<!---col 2--->
| rowspan="2" | [[Super high frequency|Super high<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1 [[Decimetre|dm]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 3&nbsp;GHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 12.4 μeV<!---col 7--->
|-
| rowspan="2" | UHF<!---col 2--->
| rowspan="2" | [[Ultra high frequency|Ultra high<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1  [[Metre|m]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 300 [[Megahertz|MHz]]<!---col 6--->
| rowspan="2" style="text-align:right;" | 1.24 μeV<!---col 7--->
|-
| rowspan="16" | [[Radio wave|Radio<br />waves]]<ref name="ITU-WRC-15">Article 2 [https://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-WRC.12-2015-PDF-E.pdf#page=6.34 "Final Acts WRC-15: World Radiocommunication Conference"], [[International Telecommunication Union]]
Geneva, 2015</ref><!---col 1--->
| rowspan="2" | VHF<!---col 2--->
| rowspan="2" | [[Very high frequency|Very high<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 10 m<!---col 5--->
| rowspan="2" style="text-align:right;" | 30&nbsp;MHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 124 [[neV]]<!---col 7--->
|-
| rowspan="2" | HF<!---col 2--->
| rowspan="2" | [[High frequency|High<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 100 m<!---col 5--->
| rowspan="2" style="text-align:right;" | 3&nbsp;MHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 12.4 neV<!---col 7--->
|-
| rowspan="2" | MF<!---col 2--->
| rowspan="2" | [[Medium frequency|Medium<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1 [[Kilometre|km]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 300 [[kilohertz|kHz]]<!---col 6--->
| rowspan="2" style="text-align:right;" | 1.24 neV<!---col 7--->
|-
| rowspan="2" | LF<!---col 2--->
| rowspan="2" | [[Low frequency|Low<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 10&nbsp;km<!---col 5--->
| rowspan="2" style="text-align:right;" | 30&nbsp;kHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 124 [[peV]]<!---col 7--->
|-
| rowspan="2" | VLF<!---col 2--->
| rowspan="2" | [[Very low frequency|Very low<br />frequency]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 100&nbsp;km<!---col 5--->
| rowspan="2" style="text-align:right;" | 3&nbsp;kHz<!---col 6--->
| rowspan="2" style="text-align:right;" | 12.4 peV<!---col 7--->
|-
| rowspan="2" | 3<!---col 2--->
| rowspan="2" | [[Ultra low frequency|Band 3]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 1 [[Megametre|Mm]]<!---col 5--->
| rowspan="2" style="text-align:right;" | 300 [[hertz|Hz]]<!---col 6--->
| rowspan="2" style="text-align:right;" | 1.24 peV<!---col 7--->
|-
| rowspan="2" | 2<!---col 2--->
| rowspan="2" | [[Super low frequency|Band 2]]<!---col 3--->
|-
| rowspan="2" style="text-align:right;" | 10&nbsp;Mm<!---col 5--->
| rowspan="2" style="text-align:right;" | 30&nbsp;Hz<!---col 6--->
| rowspan="2" style="text-align:right;" | 124 [[feV]]<!---col 7--->
|-
| rowspan="2" | 1<!---col 2--->
| rowspan="2" | [[Extremely low frequency|Band 1]]<!---col 3--->
|-
| style="text-align:right;" | 100&nbsp;Mm<!---col 5--->
| style="text-align:right;" | 3&nbsp;Hz<!---col 6--->
| style="text-align:right;" | 12.4 feV<!---col 7--->
|-
| colspan=7 | Sources<ref name=ucdavis>[http://cbst.ucdavis.edu/education/courses/winter-2006-IST8A/ist8a_2006_01_09light.pdf What is Light?] {{webarchive |url=https://web.archive.org/web/20131205005843/http://cbst.ucdavis.edu/education/courses/winter-2006-IST8A/ist8a_2006_01_09light.pdf |date=December 5, 2013 }} – [[UC Davis]] lecture slides</ref><ref name=Elert>{{cite web |author=Elert, Glenn |url=https://physics.info/em-spectrum/ |title=The Electromagnetic Spectrum |work=The Physics Hypertextbook |access-date=2022-01-21 |archive-date=2022-01-21 |archive-url=https://web.archive.org/web/20220121220019/https://physics.info/em-spectrum/ |url-status=live }}</ref><ref name=vlf>{{cite web |author=Stimac, Tomislav |url=http://www.vlf.it/frequency/bands.html |title=Definition of frequency bands (VLF, ELF... etc.) |publisher=vlf.it |access-date=2022-01-21 |archive-date=2010-04-30 |archive-url=https://web.archive.org/web/20100430012219/http://www.vlf.it/frequency/bands.html |url-status=live }}</ref> Table shows the lower frequency limits (and higher wavelength limits) for the specified class
{| class="wikitable mw-collapsible innercollapse" |
|+ class="nowrap" |Explanation of units and prefixes. 
|-
!Unit
!Abbreviation
!Name
!'''Scale'''
|-
|Wavelength
|pm
|picometer
|{{val|1|e=-12}} meters
|-
|Wavelength
|nm
|nanometer
|{{val|1|e=-9}} meters
|-
|Wavelength
|μm
|micrometer
|{{val|1|e=-6}} meters
|-
|Wavelength
|mm
|millimeter
|{{val|1|e=-3}} meters
|-
|Wavelength
|cm
|centimeter
|{{val|1|e=-2}} meters
|-
|Wavelength
|dm
|decimeter
|{{val|1|e=-1}} meters
|-
|Wavelength
|m
|meter
|1 meter
|-
|Wavelength
|km
|kilometer
|{{val|1|e=3}} meters
|-
|Wavelength
|Mm
|megameter
|{{val|1|e=6}} meters
|-
|Frequency
|EHz
|exaHertz
|{{val|1|e=18}} hertz
|-
|Frequency
|PHz
|petaHertz
|{{val|1|e=15}} hertz
|-
|Frequency
|THz
|teraHertz
|{{val|1|e=12}} hertz
|-
|Frequency
|GHz
|gigaHertz
|{{val|1|e=9}} hertz
|-
|Frequency
|MHz
|megaHertz
|{{val|1|e=6}} hertz
|-
|Frequency
|KHz
|kiloHertz
|{{val|1|e=3}} hertz
|-
|Frequency
|Hz
|Hertz
|1 Hertz
|-
|Energy Per  Photon
|keV
|kilo-electronvolt
|{{val|1|e=3}} electronvolts
|-
|Energy Per  Photon
|eV
|electronvolt
|1 electronvolt
|-
|Energy Per  Photon
|meV
|milli-electronvolt
|{{val|1|e=-3}} electronvolts
|-
|Energy Per  Photon
|μeV
|micro-electronvolt
|{{val|1|e=-6}}electronvolts
|-
|Energy Per  Photon
|neV
|nano-electronvolt
|{{val|1|e=-9}} electronvolts
|-
|Energy Per  Photon
|peV
|pico-electronvolt
|{{val|1|e=-12}}  electronvolts
|-
|Energy  Per Photon
|feV 
|femto-electronvolt
|{{val|1|e=-15}}  electronvolts
|}
|}
=== Rationale for names ===
Electromagnetic radiation interacts with matter in different ways across the spectrum. These types of interaction are so different that historically different names have been applied to different parts of the spectrum, as though these were different types of radiation. Thus, although these "different kinds" of electromagnetic radiation form a quantitatively continuous spectrum of frequencies and wavelengths, the spectrum remains divided for practical reasons arising from these qualitative interaction differences.

{| class="wikitable" width:70%; font-size:95%;
|+Electromagnetic radiation interaction with matter
|-
! Region of the spectrum
! Main interactions with matter
|-
|[[Radio wave|Radio]]
|Collective oscillation of charge carriers in bulk material ([[plasma oscillation]]). An example would be the oscillatory travels of the electrons in an [[antenna (radio)|antenna]].
|-
|nowrap|[[Microwave]] through far [[infrared]]
|Plasma oscillation, molecular rotation
|-
|Near [[infrared]]
|Molecular vibration, plasma oscillation (in metals only)
|-
|[[Light|Visible]]
|Molecular electron excitation (including pigment molecules found in the human retina), plasma oscillations (in metals only)
|-
|[[Ultraviolet]]
|Excitation of molecular and atomic valence electrons, including ejection of the electrons ([[photoelectric effect]])
|-
|[[X-ray]]s
|Excitation and ejection of core atomic electrons, [[Compton scattering]] (for low atomic numbers)
|-
|[[Gamma ray]]s
|Energetic ejection of core electrons in heavy elements, Compton scattering (for all atomic numbers), excitation of atomic nuclei, including dissociation of nuclei
|-
|nowrap|High-energy [[gamma ray]]s
|Creation of [[Virtual pair|particle-antiparticle pairs]]. At very high energies a single photon can create a shower of high-energy particles and antiparticles upon interaction with matter.
|}