Infrared radiation:Infrared radiation is electromagnetic radiation with a wavelength longer than that of visible light, but shorter than that of terahertz waves. It is emitted by all objects with a temperature above absolute zero and is thus sometimes also referred to as thermal radiation. Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers (nm) to 1 millimeter (mm). This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz.
