Which of the following describes a key principle behind RADAR technology?

The key principle behind RADAR technology is the use of radio waves that are transmitted and then reflected off objects. RADAR operates by sending out a signal in the form of radio waves, and when these waves encounter an object, they bounce back. The system then analyzes the time it takes for the waves to return and the frequency shift of the reflected waves to determine distance, speed, and other characteristics of the target. This capability makes RADAR extremely effective for applications such as air traffic control, weather monitoring, and military surveillance.

In contrast, the other options do not accurately represent the fundamental workings of RADAR. While light waves are indeed used in LIDAR technology, they do not play a role in RADAR. Sound waves are utilized in different forms of measurement like sonar, but they do not contribute to RADAR's functioning. Lastly, thermal imaging relies on detecting heat rather than radio waves, making it completely separate from RADAR technology. Thus, the focus on radio waves reflected off objects is what defines how RADAR operates.