![]() There is no universally accepted definition of the range of infrared radiation. ![]() Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops, remote temperature sensing, short-range wireless communication, spectroscopy, and weather forecasting.ĭefinition and relationship to the electromagnetic spectrum Humans at normal body temperature radiate chiefly at wavelengths around 10 μm. Military and civilian applications include target acquisition, surveillance, night vision, homing, and tracking. Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, to assist firefighting, and to detect the overheating of electrical components. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space such as molecular clouds, to detect objects such as planets, and to view highly red-shifted objects from the early days of the universe. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. Infrared radiation is used in industrial, scientific, military, commercial, and medical applications. Infrared spectroscopy examines absorption and transmission of photons in the infrared range. It excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared radiation is emitted or absorbed by molecules when changing rotational-vibrational movements. The balance between absorbed and emitted infrared radiation has an important effect on Earth's climate. Slightly more than half of the energy from the Sun was eventually found, through Herschel's studies, to arrive on Earth in the form of infrared. In 1800 the astronomer Sir William Herschel discovered that infrared radiation is a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. It was long known that fires emit invisible heat in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. As a form of electromagnetic radiation, IR carries energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. Īlmost all black-body radiation from objects near room temperature is at the IR band. Longer IR wavelengths (30–100 μm) are sometimes included as part of the terahertz radiation band. IR is commonly divided between longer-wavelength thermal IR, emitted from terrestrial sources, and shorter-wavelength IR or near-IR, part of the solar spectrum. ![]() IR is generally understood to encompass wavelengths from around 750 nm to 1000 μm (400 THz to 300 GHz). Infrared ( IR sometimes called infrared light) is electromagnetic radiation (EMR) in the spectral band between microwaves and visible light (the nominal red edge of the visible spectrum). This pseudocolor infrared space telescope image has blue, green, and red corresponding to wavelengths of 3.4, 4.6, and 12 μm, respectively. A false-color image of two people taken in long-wavelength infrared (body-temperature thermal) radiation. For other uses, see Infrared (disambiguation).
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