Infrared

Infrared (IR) radiation is a type of electromagnetic radiation (a wave with electricity) . The wave is longer than light which humans can see and shorter than microwaves. The word infrared means below red. It comes from the Latin word infra (meaning below) and the English word red. (Infrared light has a frequency below the frequency of red light.) Red light has the longest wavelength that human eyes can see. Infrared waves cannot be seen by the eye.

Near-infrared waves are between 800 nm and 1.4 µm. Most infrared from the Sun is near-infrared. Thermal imaging is mostly done with thermal radiation waves between 8 and 15 µm.

People sense infrared as heat.

Most remote controls use infrared to send the control signals. Many missiles for anti-aircraft warfare find their target by infrared.