infrared
Americannoun
adjective
noun
adjective
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Relating to the invisible part of the electromagnetic spectrum with wavelengths longer than those of visible red light but shorter than those of microwaves.
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See more at electromagnetic spectrum
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.
Etymology
Origin of infrared
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Light from extremely distant objects such as J0100+2802 has been stretched into infrared wavelengths due to the expansion of the universe.
From Science Daily
Low-energy infrared photons do not have enough energy to activate electrons, while high-energy photons such as blue light lose their extra energy as heat.
From Science Daily
It sends data back by emitting tiny pulses of infrared light that encode electrical signals from the brain.
From Science Daily
To understand how mosquitoes navigate, scientists used 3D infrared cameras to observe how the insects moved around objects using visual signals and carbon dioxide.
From Science Daily
Visible light shows what's happening on a surface, X-rays expose what lies inside, and infrared detects heat being emitted.
From Science Daily
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
