Infrared radiation or "black light" is electromagnetic radiation in the infrared portion of the electromagnetic spectrum. It consists of light which has a longer wavelength than the human eye can detect (that is, above 8,000 angstroms) Infra, meaning below in Latin, is used because the frequencies of the infrared are below those of the red color. Infrared is used in communications by optical fibers (wavelength 1550 nm), in lamps to keep food warm, in military detection equipment (for example because the heat of the human body can be perceived as an infrared radiation around 10 µms).