Learn in the textbookDetection Devices (Light, Electromagnetic, and Motion Sensors)
DefinitionAn infrared sensor (赤外線センサー) detects infrared light, which has a longer wavelength than visible light and cannot be seen by the human eye.
ExplanationAny object with a temperature gives off infrared light that depends on how warm it is. An infrared sensor reads the amount of this infrared and how it changes, so it can tell when people come and go, or how warm an object is, even in the dark. It is found in the motion detectors of lights that switch on as someone walks up, and also in the part of a TV that picks up the infrared signal sent by the remote control.
AnalogyIt is like skin so sensitive to heat that it can feel a person's warmth even in total darkness.
Memory hook"Infra" is Latin for "below": infrared sits just below red in frequency, past the edge of what the eye can see.