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

/ ĭn′frə-rĕd′ /

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

This technology, called functional near-infrared spectroscopy, is the same that allows pulse oximeters to measure oxygen levels in the blood.

From Science News

The operator gets a real-time view of what Spot sees and hears through its onboard sensors, which include an infrared camera.

From Popular-Science

Wi-Charge’s PowerPuck system employs infrared beams that can power low-draw devices from up to 30 feet away without the power level dropping as you move further away.

From Popular-Science

We suggest reaching for a ceramic, porcelain, or infrared dryer, which will gently dry your hair without sucking up healthy moisture.

From Popular-Science

He and his team are now looking at another type of light called the cosmic infrared background.

From Science News For Students

Therefore, it is not possible for any F-35 schedule to include a video data link  or infrared pointer at this point.

From The Daily Beast

Some pilots consider the infrared marker to be crucial to the close air-support mission to support ground troops.

From The Daily Beast

Infrared light does not have a color which means it cannot be seen by the human eye.

From The Daily Beast

Unlike humans, it can watch for days, even years, watch an entire city, zoom in close, use heat sensors and infrared.

From The Daily Beast

Helicopters equipped with infrared equipment flew over the area.

From The Daily Beast

It was an air-view of the city of Zurb—taken, the high priest explained, by infrared light from an airboat over the city at night.

From Project Gutenberg

It boils liquid metal and cooks out energy from the infrared right through to hard radiation.

From Project Gutenberg

Anyone leaving their Buggy would interrupt an infrared beam and stop the ride system.

From Project Gutenberg

The film registers whatever the infrared searchlight illuminates.

From Project Gutenberg

Thanks to the goggles, both of them could see the normally invisible beams of the infrared flashlight.

From Project Gutenberg

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