Microwave sensors detect movement by emitting microwave energy and bouncing it off objects, then measuring the frequency of returned waves.

• A. True
• B. False
• C. They detect heat signatures only
• D. They rely on visible light

Answer: (A)

Microwave motion sensing works by sending out microwave energy like a tiny radar unit and listening for reflections. When an object moves, the reflected microwaves experience a Doppler shift—a change in frequency—compared to what was emitted. The sensor compares the transmitted frequency to the received frequency, and that shift flags motion and can indicate speed. This is different from heat-based detectors (which sense infrared) and from systems that rely on visible light. Microwave sensors can often detect movement through certain nonmetallic barriers, which is why they’re common in alarm installations. So the description of emitting microwaves, bouncing them off objects, and measuring the returned signal’s frequency accurately captures how these sensors detect movement.