What best describes the difference between active and passive radar in air defense?

• A. Active radar emits RF energy and transmits its own signal; passive radar relies on other emissions or non-cooperative sources for detection.
• B. Active radar relies on external signals to detect targets.
• C. Passive radar emits RF energy and transmits its own signal.
• D. Passive radar detects targets without using any external emissions.

Answer: (A)

The main idea is who provides the illumination for detecting targets. In active radar, the system emits RF energy of its own and then listens for echoes to determine range, bearing, and speed. In passive radar, there is no own emission; it relies on signals from other, non-cooperative transmitters (such as commercial broadcasts or other radars) and detects targets by analyzing how those signals interact with objects or by correlating received signals with the known transmissions.

So the best description is that active radar transmits its own signal, while passive radar relies on external emissions for detection. The other statements mix up which system emits energy or suggests no external source is involved, which isn’t accurate.