Infrared waves can be defined as electromagnetic waves whose wavelengths fall under the infrared region. The wavelengths of infrared waves range from 700 nanometres to one millimetre. Therefore, it can be understood that an infrared wave has a longer wavelength than that of visible light (and also an ultraviolet wave). Also, it is important to note that the frequencies of infrared waves are always higher than that of an electromagnetic wave falling under the visible spectrum or the ultraviolet spectrum. The frequency of an infrared wave can range from 300 gigahertz to about 400 terahertz.
Common examples of infrared waves include long-wave infrared radiation (often abbreviated to LWIR) and short-wave infrared radiation (often abbreviated to SWIR). Common television remotes emit signals in the form of short-wave infrared radiation. The heat that emanates from fires and lit charcoal is transmitted via long-wave infrared radiation.