The infrared portion of the electromagnetic spectrum can be divided into three regions of infrared waves, all of which have different lengths. Far-infrared waves measure from 300 gigahertz to 30 terahertz, while mid-infrared waves range from 30 terahertz to 120 terahertz. Near-infrared waves range from 120 to 400 terahertz.
Infrared light has longer wavelengths compared with visible light. Its range of wavelengths corresponds to a frequency range of approximately 300 gigahertz to 400 terahertz. It includes most of the thermal radiation emitted by objects near room temperature. Infrared light is emitted or absorbed by molecules that change their rotational movements.