Which camera is an example of a passive sensor?

• A. RGB
• B. LIDAR
• C. SAR
• D. Thermal

Answer: (A)

A passive sensor is one that collects energy from the scene without emitting anything itself. An RGB camera fits this description perfectly because it only captures visible light that is reflected off objects; it does not send out light or signals.

In contrast, LIDAR and SAR actively emit energy—laser light and radio waves, respectively—and then listen for the echoes, which makes them active sensing methods. Thermal cameras detect infrared radiation emitted by objects; they don’t emit energy either, so they are also passive in that sense, but in the context of a standard “camera” example, the classic passive imaging device is the RGB camera.