What principle does radar technology operate on?

Radar technology operates on the principle of emitting radio waves and measuring the time it takes for those waves to bounce back after hitting an object. When radar transmits radio waves, they travel through the air until they encounter an object, such as a vehicle. The waves then reflect off the object and return to the radar unit. By measuring the time it takes for the waves to return, the radar system can calculate the distance to the object as well as its speed, based on the changes in frequency of the returning waves due to the Doppler effect.

This principle is fundamental to the functioning of radar, making it an effective tool for speed detection in law enforcement and various applications, such as aviation and weather monitoring. The other options do not accurately describe how radar works; for example, sound waves are used in sonar technology, while thermal energy detection involves sensing heat rather than using electromagnetic waves like radar does.