BSL Physics Glossary - infrared radiation - definition
On the electromagnetic spectrum there is the area of visible light. Beyond this there are invisible waves such as infrared radiation. The wavelengths of infrared vary from 700 to 1,500 nanometres (nm).
Infrared waves are used in many ways. For example you have a remote control to control your TV. You can't see the infrared light which comes from the remote, but it changes the channel. Another use is for the police to spot vehicles from a helicopter. At night time the police can't see what's on the ground, but with an infrared camera they can identify moving cars because they show up as heat images. The white parts of the image are the hottest part - usually the wheels. So the police can track the moving vehicle in the dark. Another example of the use of infrared radiation is after an earthquake when buildings have collapsed, trapping people under the bricks. With an infrared camera it is possible to find the warm bodies quickly.