Spectrum has since been applied by analogy to topics outside optics. Thus, one might talk about the "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 termspectrum are sometimes misleading. For instance, a singleleft–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 ofspectrum there is a unifying theme between the extremes at either end. This was not always true in older usage.
The prefix "spectro-" is used to form words relating to spectra. For example, aspectrometer is a device used to record spectra andspectroscopy is the use of a spectrometer forchemical analysis.
The concept was later expanded to otherwaves, such assound waves andsea waves that also present a variety of frequencies and wavelengths (e.g.,noise spectrum,sea wave spectrum). Starting fromFourier analysis, the concept of spectrum expanded tosignal theory, where the signal can be graphed as a function of frequency andinformation can be placed in selected ranges of frequency. Presently, any quantity directly dependent on, and measurable along therange of, a continuousindependent variable can be graphed along itsrange orspectrum. Examples are the range ofelectron energy inelectron spectroscopy or the range ofmass-to-charge ratio inmass spectrometry.
In psychiatry, thespectrum approach uses the term spectrum to describe a range of linked conditions, sometimes also extending to include singular symptoms andtraits. For example, theautism spectrum describes a range of conditions classified asneurodevelopmental disorders.
Insocial science,economic spectrum is used to indicate the range of social class along some indicator of wealth or income. Inpolitical science, the termpolitical 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.
Look upspectrum in Wiktionary, the free dictionary.
^"Spectrum".The American Heritage Dictionary of the English Language (4th ed.). Houghton Mifflin Company. 2004. Archived fromthe original on February 23, 2008. RetrievedJanuary 25, 2008.
^ OpenStax Astronomy, "Spectroscopy in Astronomy". OpenStax CNX. September 29, 2016"OpenStax CNX".Archived from the original on February 17, 2017. RetrievedFebruary 17, 2017.
