Line spectrum

Article By:

Baird, Christopher S. Department of Chemistry and Physics, West Texas A&M University, Canyon, Texas.

Last reviewed:March 2022

DOI:https://doi.org/10.1036/1097-8542.383800

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• Line spectrum, published January 2020:Download PDF Get Adobe Acrobat Reader

The spectrum of a beam of light when only a few isolated colors are present. A beam of light (technically, a beam of electromagnetic radiation) typically contains a mixture of pure colors. The particular pure colors that are present in the beam depend on the nature of the source that created the light. By carefully identifying these colors, information about the source can be deduced. The most direct way to identify these colors is to spatially separate and spread the colors out along a uniform frequency or wavelength scale. The result is the spectrum of the light. One particular type of light beam has a spectrum called a line spectrum, which consists of only a few, isolated, pure colors. In practice, a device called a grating is typically used to form the spectrum of a particular beam of light. Because gratings consist of a uniform set of long, parallel elements such as slits, each isolated color in the resulting spectrum shows up visually as a line. Therefore, a line spectrum in practice appears as a sparse collection of thin, colored lines on a black background (Fig. 1). See also: Color; Electromagnetic radiation; Frequency (wave motion); Light; Spectrum

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