Arizona Drivers Permit Practice Exam Guide

Which technology is most commonly used in passive infrared (PIR) motion detectors for security systems?

Emitting ultrasonic waves and measuring the reflection Emitting microwaves and measuring the Doppler shift Detecting the heat energy emitted by an intruder Using a laser beam broken by an object

Correct Answer:

Detecting the heat energy emitted by an intruder

Explanation:

PIR detectors are 'passive' because they do not emit energy; they detect the infrared heat energy radiating from moving bodies.

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