Electromagnetic spectrum: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Alex MacDonald
No edit summary
mNo edit summary
 
(22 intermediate revisions by 8 users not shown)
Line 1: Line 1:
The '''Electromagnetic Spectrum''' is the name given to the range of [[Electromagnetic radiation]] covering all [[frequencies]] and [[wavelengths]]. It includes [[radio]] and [[TV]] transmission, [[Microwaves]], [[Infrared]], visible [[light]], [[Ultraviolet]], [[X-rays]], and [[Gamma rays]].
{{subpages}}
{{TOC|right}}




The '''Electromagnetic Spectrum''' is the name given to the range of [[electromagnetic wave]]s covering all [[frequencies]] and [[wavelengths]]. It includes [[radio]] and [[television]] transmission, [[Microwaves]], [[Infrared]], visible [[light]], [[Ultraviolet]], [[X-rays]], and [[Gamma rays]]. The relatively new (since the 1990s) technology of terahertz (THz) radiation can be thought of as occupying a gap between infrared radiation and microwaves, covering frequencies of roughly 0.1 to 10 THz.
{{Image|ElectroMagneticSpectrum.JPG|left|300px|Electromagnetic spectrum}}
=== Electromagnetic radiation ===
=== Electromagnetic radiation ===
All electromagnetic radiation can be described in terms of its [[Energy]] (E), [[frequency]] (f), [[wavenumber]] (v'), or [[wavelength]] (<math>\lambda</math>). These properties are all related by the following equations:


:All electromagnetic radiation can be described in terms of its [[Energy]] (E), [[frequency]] (f) or [[wavelength]] (<math>\lambda</math>). These properties are all related by the following equations:
:<math>\lambda = \frac{c}{f}  \,\!</math> ,  
 
:<math>\lambda = \frac{c}{f}  \,\!</math> ,
 
:<math>E=hf \,\!</math> ,
:<math>E=hf \,\!</math> ,


where c = 299,792,458 m/s (the [[speed of light]]) and h = 6.626 x 10<sup>-34</sup> Js ([[Planck's constant]])
where c = 299,792,458 m/s (the [[speed of light]]) and h = 6.626 x 10<sup>-34</sup> Js ([[Planck's constant]])


:As well as the wavelike properties of EM radiation several effects particularly of the emission and absorption of light behave like particles. That is, the energy carried by light waves is packaged in discrete bundles called [[photons]] or [[quanta]]. This [[wave-particle duality]] is described in [[quantum electrodynamics]], a theory which began to be developed around 1930.
As well as the wavelike properties of EM radiation several effects particularly of the emission and absorption of light behave like particles. That is, the energy carried by light waves is packaged in discrete bundles called [[photons]] or [[quanta]]. The particle character of light  is described in [[quantum electrodynamics]], a theory which began with Dirac's work of 1927.<ref>P.A.M. Dirac, Proc. Royal Society (London), ''The Quantum Theory of the Emission and Absorption of Radiation'', vol. '''A114''', p. 243 (1927)</ref>
 
{{seealso|electromagnetic wave}}


==Electromagnetic spectrum as a resource==
Especially in [[radio]] and [[radar]] frequencies, the electromagnetic spectrum can be a scarce and valuable resource, since a given frequency in a given geographic area can often be used only for one purpose. This is a classic requisite of a [[technical monopoly]]. If a frequency is in use for commercial [[television]], than it cannot be used for [[cellular telephony]]. In [[electronic warfare]], there may be difficult tradeoffs between letting an enemy use a radio frequency for his own purposes while one's own side is gaining signals intelligence from it, or [[electronic warfare#electronic attack|jamming]] to deny its use for [[command and control]].


== References ==
See [[electromagnetic spectrum management]] for the policy, management, and commercialization of parts of the spectrum.


== Reference ==
<references />
==Further reading==
* Young and Freedman. ''University Physics''. Addison-Wesley Publishing Company. ISBN 0-201-31132-1
* Young and Freedman. ''University Physics''. Addison-Wesley Publishing Company. ISBN 0-201-31132-1
* [http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html NASA introduction to electromagnetic spectrum]
* [http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html NASA introduction to electromagnetic spectrum][[Category:Suggestion Bot Tag]]
 
[[Category:Physics]]
[[Category:CZLive]]
[[Category:Physics Workgroup]]

Latest revision as of 07:01, 11 August 2024

This article is a stub and thus not approved.
Main Article
Discussion
Related Articles  [?]
Bibliography  [?]
External Links  [?]
Citable Version  [?]
 
This editable Main Article is under development and subject to a disclaimer.


The Electromagnetic Spectrum is the name given to the range of electromagnetic waves covering all frequencies and wavelengths. It includes radio and television transmission, Microwaves, Infrared, visible light, Ultraviolet, X-rays, and Gamma rays. The relatively new (since the 1990s) technology of terahertz (THz) radiation can be thought of as occupying a gap between infrared radiation and microwaves, covering frequencies of roughly 0.1 to 10 THz.

Electromagnetic spectrum

Electromagnetic radiation

All electromagnetic radiation can be described in terms of its Energy (E), frequency (f), wavenumber (v'), or wavelength (). These properties are all related by the following equations:

,
,

where c = 299,792,458 m/s (the speed of light) and h = 6.626 x 10-34 Js (Planck's constant)

As well as the wavelike properties of EM radiation several effects particularly of the emission and absorption of light behave like particles. That is, the energy carried by light waves is packaged in discrete bundles called photons or quanta. The particle character of light is described in quantum electrodynamics, a theory which began with Dirac's work of 1927.[1]

See also: electromagnetic wave

Electromagnetic spectrum as a resource

Especially in radio and radar frequencies, the electromagnetic spectrum can be a scarce and valuable resource, since a given frequency in a given geographic area can often be used only for one purpose. This is a classic requisite of a technical monopoly. If a frequency is in use for commercial television, than it cannot be used for cellular telephony. In electronic warfare, there may be difficult tradeoffs between letting an enemy use a radio frequency for his own purposes while one's own side is gaining signals intelligence from it, or jamming to deny its use for command and control.

See electromagnetic spectrum management for the policy, management, and commercialization of parts of the spectrum.

Reference

  1. P.A.M. Dirac, Proc. Royal Society (London), The Quantum Theory of the Emission and Absorption of Radiation, vol. A114, p. 243 (1927)

Further reading