infrared radiation Electromagnetic radiation which has a wavelength between 0.7 μm and 100 μm. See also NEAR-INFRARED; MID-INFRARED; REFLECTED INFRARED; and THERMAL INFRARED.

infrared radiation (IR) Electromagnetic radiation that produces a sensation of heat emitted by hot objects. An example is seen in the glowing wires of a toaster. Intermediate in energy between visible light and microwaves, its wavelength range is about 750nm to 1mm. It has applications in astronomy, medicine and warfare (for targeting the enemy at night).

infrared radiation (in-fră-red) n. the band of electromagnetic radiation that is longer in wavelength than the red of the visible spectrum and is responsible for the transmission of radiant heat. It may be used in physiotherapy to warm tissues, reduce pain, and improve circulation.