Infrared Infrared radiation , or simply infrared or IR , is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is, therefore, invisible, although it is sometimes loosely called infrared light . It extends from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1000000 nm (300 GHz) (although people can see infrared up to at least 1050 nm in experiments). Most of the thermal radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon. Infrared was discovered in 1800 by astronomer Sir William Herschel, who discovered a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitte