Infrared light has a range of wavelengths. ‘Near infrared’ has shorter wavelengths and is used for devices such as night vision goggles. ‘Far infrared’ has longer wavelengths and is used for things such as thermal imaging. In the thermal image above the left hand cup holds a hot drink and the right hand cup a cold drink. The coolest parts are dark blue and the hottest parts have been coloured white to signal a temperature of 55° Celsuis and beyond.
Infrared can also be used for some short range ‘line of sight’ communication, such as TV remote controls.