Spectrum

Source: Wikipedia, the free encyclopedia.

This article is about variation within extremes. For other uses, see Spectrum (disambiguation).
The spectrum in a rainbow

A spectrum (pl.: spectra or spectrums)

visible light after passing through a prism. As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum
. It thereby became a mapping of a range of magnitudes (wavelengths) to a range of qualities, which are the perceived "colors of the rainbow" and other properties which correspond to wavelengths that lie outside of the visible light spectrum.

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 term spectrum are sometimes misleading. For instance, a single 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

On Vision and Colors
.

The prefix "spectro-" is used to form words relating to spectra. For example, a

chemical analysis
.

Physical sciences

This section is an excerpt from Spectrum (physical sciences).[edit]
Diagram illustrating the electromagnetic spectrum

In the

physical sciences, the term spectrum was introduced first into optics by Isaac Newton in the 17th century, referring to the range of colors observed when white light was dispersed through a prism.[2][3]
Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.

Later it expanded to apply to other
power spectrum can be analyzed and processed. The term now applies to any signal that can be measured or decomposed along a continuous variable, such as energy in electron spectroscopy or mass-to-charge ratio in mass spectrometry
. Spectrum is also used to refer to a graphical representation of the signal as a function of the dependent variable.

Biological science

Gram-positive bacteria such as Staphylococcus aureus.[6]

In psychiatry, the

spectrum approach uses the term spectrum to describe a range of linked conditions, sometimes also extending to include singular symptoms and traits. For example, the autism spectrum describes a range of conditions classified as neurodevelopmental disorders
.

Mathematics

See also: Spectrum (disambiguation) § Mathematics

In

eigenvalues
of the matrix.

In functional analysis, the concept of the spectrum of a bounded operator is a generalization of the eigenvalue concept for matrices.

In

generalized cohomology theory
.

Social science

Nolan chart of the political spectrum using (red leftism and blue rightism
) coding

In

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

Look up spectrum in Wiktionary, the free dictionary.
  1. ^ Dictionary.com Archived February 23, 2008, at the Wayback Machine. The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. (accessed: January 25, 2008).
  2. ^ Open access icon OpenStax Astronomy, "Spectroscopy in Astronomy". OpenStax CNX. September 29, 2016 "OpenStax CNX". Archived from the original on February 17, 2017. Retrieved February 17, 2017.
  3. doi:10.1098/rstl.1671.0072. The word "spectrum" to describe a band of colors that has been produced, by refraction or diffraction
    , from a beam of light first appears on p. 3076.
  4. ISBN 978-0-8036-8313-6
    .
  5. ^
    ISBN 0-443-05249 2
    )
  6. PMID 17034644
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Spectrum&oldid=1197457584"