Click here to find the answer Security systems often use Passive Infrared detectors, or PIR detectors, to detect the presence of someone in the room. The PIR detector, which is positioned high up in the room, can detect a moving heat source and sends an electrical signal to the alarm control panel, which activates the alarm. All objects will either emit or absorb heat. It depends whether they are hotter or colder than their surroundings. This way of transferring heat is called Radiation.
Heat is infrared radiation.
The hotter the object - the more infrared radiation it emits. The hottest object in our solar system is the Sun. We receive infrared radiation from the Sun. They say you should wear white clothes in the summer. Tony decided to do an experiment to find out if different surfaces made a difference to how quickly heat was lost.