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Overview

spectrum

1 A range of electromagnetic energies arranged in order of wavelength or frequency (see electromagnetic spectrum). The emission spectrum of a body or substance is the range of ...

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A Dictionary of Construction, Surveying and Civil Engineering

Reference type:
Subject Reference
Current Version:
2013

... A range, particularly the distribution of colour...

spectrum

spectrum   Reference library

Garner’s Modern English Usage (4 ed.)

Reference type:
Subject Reference
Current Version:
2016

... . The plural spectra vastly predominates over spectrums in print sources and has consistently done so since the 18th century. See plurals (b) . Current ratio:...

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A Dictionary of Biology (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
211 words

...a substance capable of emitting a spectrum these are in exactly the same positions in the spectrum as the emission lines and bands would occur in the emission spectrum. Emission and absorption spectra may show a continuous spectrum , a line spectrum , or a band spectrum . A continuous spectrum contains an unbroken sequence of frequencies over a relatively wide range; it is produced by incandescent solids, liquids, and compressed gases. Line spectra are discontinuous lines produced by excited atoms and ions as they fall back to a lower energy level. Band...

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A Dictionary of Electronics and Electrical Engineering (5 ed.)

Reference type:
Subject Reference
Current Version:
2018

... The range of possible frequencies that a particular (electrical) signal can have. For example, the audio spectrum is generally considered to extend from 20 hertz to 20 kilohertz, so a given audio signal will be found in this range, and a given instrument will have its own spectrum of frequencies or spectral response within this range. ...

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A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

... 1. A range of electromagnetic energies arranged in order of wavelength or frequency ( see electromagnetic spectrum ). The emission spectrum of a body or substance is the range of radiations it emits when it is heated, is bombarded by electrons or ions, or absorbs photons. The absorption spectrum of a substance consists of dark lines or bands in a continuous spectrum, each line being a wavelength or group of wavelengths at which light is removed from the continuous spectrum by the absorbing medium. These lines and bands are at the same...

spectrum

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A Dictionary of Nursing (7 ed.)

Reference type:
Subject Reference
Current Version:
2017
Subject:
Medicine and health
Length:
23 words

...spectrum [ spek -trŭm] n. (in pharmacology) the range of effectiveness of an antibiotic. broad s. effectiveness against a wide range of microoganisms....

spectrum

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A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
265 words
Illustration(s):
1

...spectrum of a substance is produced by examining, through the substance and through a spectroscope, a continuous spectrum of radiation. The energies removed from the continuous spectrum by the absorbing medium show up as black lines or bands. With a substance capable of emitting a spectrum, these are in exactly the same positions in the spectrum as some of the lines and bands in the emission spectrum. Spectrum. Sources of electromagnetic spectra. Emission and absorption spectra may show a continuous spectrum , a line spectrum , or a band spectrum ....

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A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
264 words

...spectrum of a body or substance is the characteristic range of radiations it emits when it is heated, bombarded by electron or ions, or absorbs photons. The absorption spectrum of a substance is produced by examining, through the substance and through a spectroscope, a continuous spectrum of radiation. The energies removed from the continuous spectrum by the absorbing medium show up as black lines or bands. With a substance capable of emitting a spectrum, these are in exactly the same positions in the spectrum as some of the lines and bands in the...

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World Encyclopedia

Reference type:
Subject Reference
Current Version:
2004
Subject:
Encyclopedias
Length:
148 words

... Arrangement of electromagnetic radiations ordered by wavelength or frequency. The visible light spectrum is a series of colours: red, orange, yellow, green, blue, indigo, and violet. Each colour corresponds to a different wavelength of light. This was first noted in 1666 by English physicist Isaac Newton . A spectrum is seen in a rainbow or when white light passes through a prism . This effect, also seen when visible light passes through a diffraction grating, produces a continuous spectrum in which all wavelengths (between certain limits) are...

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John Borwick

The Oxford Companion to Music

Reference type:
Subject Reference
Current Version:
2011
Subject:
Music
Length:
91 words

...spectrum , spectral components . The range of frequencies (wavelengths) covered by a source of waves; for example, the light spectrum can be divided into about seven distinguishable colours from red, having the longest wavelength, to violet, the shortest. Similarly, sound waves occupy a range of wavelengths from about 17 mm to 17 metres, corresponding respectively to the highest and lowest frequencies audible to the human ear. The harmonic spectrum of a musical instrument is drawn as a series of vertical lines (spectral components) showing the relative...

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A Dictionary of Geology and Earth Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2013

... ( pl. spectra ; optical emission spectrum ) A series of lines (line spectra), produced as electrons return to their original energy levels and emit excess energy as infrared, visible, or ultraviolet light of characteristic wavelengths, after atoms have been heated strongly and valence electrons in the outer shell have moved to higher energy levels. Each element has a characteristic line spectrum. The intensity of each line is related to the concentration of the element being...

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A Dictionary of Space Exploration (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...used in spectroscopy. An incandescent body gives rise to a continuous spectrum where the dispersed radiation is distributed uninterruptedly over a range of wavelengths. A gaseous element gives a line spectrum —one or more bright discrete lines at characteristic wavelengths. Molecular gases give band spectra in which there are groups of closely-packed lines. In an absorption spectrum dark lines or spaces replace the characteristic bright lines of the absorbing medium. The mass spectrum of an element is obtained from a mass spectrometer and shows the...

spectrum

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The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

... The spectrum of an object (not to be confused with the term ‘ power spectrum ’) is a plot of the measured flux of electromagnetic radiation as a function of wavelength. The most important use of spectra in cosmology is in determining redshifts . An optical spectrum is obtained by dispersing light using a diffraction grating, a set of fine, narrowly spaced lines etched on a smooth, reflective surface, or a grism, a combined diffraction grating and prism. In either case, light is separated into its component wavelengths. The spectrum thus obtained...

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A Dictionary of Psychology (4 ed.)

Reference type:
Subject Reference
Current Version:
2015

... n . Any distribution of values across a range, especially the range of colours produced by passing white light through a prism or a diffraction grating , the visible spectrum extending from a wavelength of about 390 nanometres at the short end to about 740 nm at the long end. Perceived colour depends on the balance of wavelengths across the whole visual field, and most people who are asked what colours they can see in a spectrum name the psychological primaries red, yellow, green, and blue, but the following breakdown and labelling has become...

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A Dictionary of Environment and Conservation (3 ed.)

Reference type:
Subject Reference
Current Version:
2017

... The distribution of electromagnetic radiation in order of wavelength . See also electromagnetic spectrum...

spectrum

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Oxford Dictionary of Biochemistry and Molecular Biology (2 ed.)

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Life Sciences
Length:
37 words

... ( pl. spectra ) (in physics) an arrangement of the components of a complex electromagnetic radiation (light, etc.) or sound in order of frequency or energy, thereby showing a distribution of energy among the components. —spectral ...

electric spectrum

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A Dictionary of Electronics and Electrical Engineering (5 ed.)

Reference type:
Subject Reference
Current Version:
2018

...spectrum The colour spectrum produced by an electric arc . ...

visible spectrum

visible spectrum   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
15 words

...spectrum The spectrum of electromagnetic radiations to which the human eye is...

visible spectrum

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A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
17 words

...visible spectrum The spectrum of electromagnetic radiations to which the human eye is sensitive. See colour...

electromagnetic spectrum

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A Dictionary of Geology and Earth Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2013

...spectrum The range of frequencies or wavelengths of electromagnetic radiation...

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