Electromagnetic radiation lying in the wavelength interval from 0. 7 µ to 1000 µ. Its lower limit is bounded by visible radiation, and its upper limit by microwave radiation. Most energy emitted by Earth and its atmosphere is at infrared wavelength. Infrared radiation is generated almost entirely by large-scale intramolecular processes. The triatomic gases, such as water vapor, carbon dioxide, and ozone, absorb infrared radiation and play important roles in propagating infrared radiation in the atmosphere. Abbreviated IR; also called "longwave radiation. "