Infrared (IR) radiation is a type of electromagnetic radiation (a wave with electricity) . The wave is longer than light which humans can see and shorter than microwaves. The word infrared means below red. It comes from the Latin word infra (meaning below) and the English word red. (Infrared light has a frequency below the frequency of red light.) Red light has the longest wavelength that human eyes can see. Infrared waves cannot be seen by the eye. The infrared wave is between 800 nm and 1 mm. People sense infrared as heat.
Most remote controls use infrared to send the control signals. Many missiles for anti-aircraft warfare find their target by infrared.
Telecommunications
Before Bluetooth was invented, some computers, personal digital assistants, and mobile phones were using the infrared technology to send files to other devices. Bluetooth replaced infrared in the early 2000's. Infrared is limited by the need to have both devices in a "line of sight" with each other.
Infrared lasers are used to provide the light for optical fiber communications systems. Infrared light with a wavelength around 1,330 nm (least dispersion) or 1,550 nm (best transmission) are the best choices for standard silica fibers.
Related pages
Images for kids
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A false color image of two people taken in long-wavelength infrared (body-temperature thermal) light.
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This infrared space telescope image has (false color) blue, green and red corresponding to 3.4, 4.6, and 12 µm wavelengths, respectively.
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Infrared in relation to electromagnetic spectrum
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Plot of atmospheric transmittance in part of the infrared region.
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Materials with higher emissivity appear to be hotter. In this thermal image, the ceramic cylinder appears to be hotter than its cubic container (made of silicon carbide), while in fact they have the same temperature.
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Infrared light from the LED of a remote control as recorded by a digital camera.
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Reflected light photograph in various infrared spectra to illustrate the appearance as the wavelength of light changes.
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IR Satellite picture taken 1315 Z on 15th October 2006. A frontal system can be seen in the Gulf of Mexico with embedded Cumulonimbus cloud. Shallower Cumulus and Stratocumulus can be seen off the Eastern Seaboard.
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Beta Pictoris with its planet Beta Pictoris b, the light-blue dot off-center, as seen in infrared. It combines two images, the inner disc is at 3.6 µm.
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The Arnolfini Portrait by Jan van Eyck, National Gallery, London
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Thermographic image of a snake eating a mouse
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Infrared radiation was discovered in 1800 by William Herschel.
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