infrared

Or in·fra-red

[in-fruh-red]

noun

1. the part of the invisible spectrum that is contiguous to the red end of the visible spectrum and that comprises electromagnetic radiation of wavelengths from 800 nanometers to 1 millimeter.

adjective

1. noting or pertaining to the infrared or its component rays.

   infrared radiation.

infrared

/ ˌɪnfrəˈrɛd /

noun

1. the part of the electromagnetic spectrum with a longer wavelength than light but a shorter wavelength than radio waves; radiation with wavelength between 0.8 micrometres and 1 millimetre

adjective

1. of, relating to, using, or consisting of radiation lying within the infrared

   infrared radiation

infrared

1. Relating to the invisible part of the electromagnetic spectrum with wavelengths longer than those of visible red light but shorter than those of microwaves.

2. See more at electromagnetic spectrum

Word History and Origins

Origin of infrared¹

First recorded in 1825–35; infra- + red ¹

A Closer Look

In 1800 the astronomer Sir William Herschel discovered infrared light while exploring the relationship between heat and light. Herschel used a prism to split a beam of sunlight into a spectrum and then placed a thermometer in each of the bands of light. When he placed the thermometer just outside the red band, where there was no visible color, the temperature rose, as if light were shining on the thermometer. Further experiment showed that this invisible radiation behaved like visible light in many ways; for example, it could be reflected by a mirror. Infrared radiation is simply electromagnetic radiation with a lower frequency than visible light, having longer wavelengths of 0.7 micrometer to 1 millimeter. Ultraviolet radiation, like infrared radiation, lies just outside the visible part of the spectrum, but with higher frequencies; some animals, such as bees, are capable of seeing such radiation. Both infrared and ultraviolet radiation are often referred to as forms of light, though they cannot be seen by human beings. Heat energy is often transferred in the form of infrared radiation, which is given off from an object as a result of molecular collisions within it. Molecules typically have a characteristic infrared absorption spectrum, and infrared spectroscopy is a common technique for identifying the molecular structure of substances. Astronomers similarly analyze the infrared radiation emitted by celestial bodies to determine their temperature and composition.

Example Sentences

HPF also helps reduce the impact of M-dwarf stellar activity by observing in the infrared -- a region of the spectrum where disruptive signals from the star are weaker.

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The same unusual effect appeared in these infrared data, suggesting that it is not a measurement error but a genuine feature of the universe.

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Their analysis revealed that the magnetic component of light is responsible for about 17% of the observed rotation in the visible spectrum and as much as 70% in the infrared.

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In doing so, the incoming light particles are converted to infrared light.

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Temperatures above 45 degrees Celsius can damage tissue, but the Aalto team developed a method that allows real-time temperature monitoring while heating the area with near infrared light.

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