Editing Spectrum

{{Use mdy dates|date=August 2017}}
{{About|variation within extremes}}
{{Short description|Continuous range of values, such as wavelengths in physics}}
[[File:Rainbow above Kaviskis Lake, Lithuania.jpg|thumb|The spectrum in a [[rainbow]]]]

A '''spectrum''' ({{plural form}}: '''spectra''' or '''spectrums''') is a set of related ideas, objects, or properties whose features overlap such that they blend to form a [[Continuum (measurement)|continuum]].<ref>{{cite web |url=http://dictionary.reference.com/browse/spectrum |title=Spectrum  |archive-url=https://web.archive.org/web/20080223153840/http://dictionary.reference.com/browse/spectrum |archive-date=February 23, 2008 |work=The American Heritage Dictionary of the English Language |edition=4th |publisher=Houghton Mifflin Company |year=2004 |access-date= January 25, 2008}}</ref> The word ''spectrum'' was first used scientifically in [[optics]] to describe the [[rainbow]] of colors in [[visible light]] after passing through a [[dispersive prism|prism]]. In the optical spectrum, light [[wavelength]] is viewed as continuous, and spectral colors are seen to blend into one another smoothly when organized in order of their corresponding wavelengths. As scientific understanding of light advanced, the term came to apply to the entire [[electromagnetic spectrum]], including radiation not visible to the human eye. 

''Spectrum'' has since been applied by analogy to topics outside optics. Thus, one might talk about the "[[political spectrum|spectrum of political opinion]]", or the "spectrum of activity" of a drug, or the "[[autism spectrum]]". In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions. Such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the term ''spectrum'' are sometimes misleading. For instance, a single [[left–right political spectrum|left–right spectrum]] of political opinion does not capture the full range of people's political beliefs. Political scientists use a variety of biaxial and multiaxial systems to more accurately characterize political opinion.

In most modern usages of ''spectrum'' there is a unifying theme between the extremes at either end. This was not always true in older usage.

==Etymology==
In [[Latin]], ''spectrum'' means "image" or "[[apparitional experience|apparition]]", including the meaning "[[Ghost#Terminology|spectre]]". [[Spectral evidence]] is testimony about what was done by spectres of persons not present physically, or [[hearsay]] evidence about what ghosts or apparitions of [[Satan]] said. It was used to convict a number of persons of [[witchcraft]] at [[Salem, Massachusetts]] in the late 17th century. The word "spectrum" [Spektrum] was strictly used to designate a ghostly optical [[afterimage]] by [[Johann Wolfgang von Goethe|Goethe]] in his ''[[Theory of Colours (book)|Theory of Colors]]'' and [[Arthur Schopenhauer|Schopenhauer]] in ''[[On Vision and Colors]]''.

The prefix "spectro-" is used to form words relating to spectra. For example, a [[spectrometer]] is a device used to record spectra and [[spectroscopy]] is the use of a spectrometer for [[chemical analysis]].

==Physical sciences==
{{excerpt|Spectrum (physical sciences)}}

==Biological science==
[[Antibiotic]] spectrum of activity is a component of [[Antibiotic#Classes|antibiotic classification]]. A [[broad-spectrum antibiotic]] is active against a wide range of bacteria,<ref>{{Cite book |last=Taber |first=Clarence Wilbur |title=Taber's cyclopedic medical dictionary |date=1993 |publisher=F. A. Davis |isbn=978-0-8036-8313-6 |editor-last=Thomas |editor-first=Clayton L. |edition=Ed. 17, illustrated, 3. print |location=Philadelphia}}</ref> whereas a [[narrow-spectrum antibiotic]] is effective against specific families of bacteria.<ref name=Hopkins>S.J. Hopkins, Drugs and Pharmacology for Nurses 12th ed., 1997 ({{ISBN|0-443-05249 2}})</ref> An example of a commonly used broad-spectrum antibiotic is [[ampicillin]].<ref name=Hopkins /> An example of a narrow spectrum antibiotic is [[Dicloxacillin]], which acts on [[beta-lactamase]]-producing [[Gram-positive]] bacteria such as ''[[Staphylococcus aureus]]''.<ref name="pmid17034644">{{cite journal |vauthors=Miranda-Novales G, Leaños-Miranda BE, Vilchis-Pérez M, Solórzano-Santos F |title=''In vitro'' activity effects of combinations of cephalothin, dicloxacillin, imipenem, vancomycin and amikacin against methicillin-resistant ''Staphylococcus'' spp. strains |journal=Ann. Clin. Microbiol. Antimicrob. |volume=5 |pages=25 |year=2006 |pmid=17034644 |pmc=1617116 |doi=10.1186/1476-0711-5-25 |doi-access=free }}</ref>

In psychiatry, the [[spectrum approach]] uses the term spectrum to describe a range of linked conditions, sometimes also extending to include singular symptoms and [[trait theory|traits]]. For example, the [[autism spectrum]] describes a range of conditions classified as [[neurodevelopmental disorder]]s.

==Mathematics==
{{See also|Spectrum (disambiguation)#Mathematics}}

In [[mathematics]], the [[spectrum of a matrix]] is the [[multiset]] of the [[eigenvalue]]s of the matrix.

In [[functional analysis]], the concept of the [[Spectrum (functional analysis)|spectrum of a bounded operator]] is a generalization of the eigenvalue concept for matrices.

In [[algebraic topology]], a [[Spectrum (topology)|spectrum]] is an object representing a [[generalized cohomology theory]].

==Social science==
[[File:Political-spectrum-multiaxis.png|thumb|A [[Nolan chart]] of the political spectrum using ([[Red#Use by political movements|red leftism]] and [[Blue#Politics|blue rightism]]) coding]]
In [[social science]], [[economic spectrum]] is used to indicate the range of social class along some indicator of wealth or income. In [[political science]], the term [[political spectrum]] refers to a system of classifying political positions in one or more dimensions, for example in a range including right wing and left wing.

==References==
{{Wiktionary}}
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[[Category:Concepts in physics]]
[[Category:Light]]
[[Category:Broad-concept articles]]