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Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. The name means "below red" (from Latin infra, "below"), red being the color of visible light of longest wavelength.

Often subdivided into near IR (NIR, 800 nm-2 μm wavelength), mid or intermediate IR (MIR or IIR, 2 - 30 μm) and far IR (FIR, 30 - 200 μm). However, these terms are not precise, and are use variously between different fields of study. Infrared radiation is often linked to heat, since objects at room temperature or above will emit radiation mostly concentrated in the mid-infrared band (see black body).


Infrared is used in night-vision equipment, when their is insufficient visible light to see an object. The radiation is detected and turned into an image on a screen, hotter objects showing up brighter, enabling the police and military to chase targets. A more common use of IR is in television remote controls. In this case it is used in preference to radio waves because it does not interfere with the television signal. IR is also employed in short-range communication among computer peripherals and personal digital assistants.