Final answer:
Radar systems use microwaves to detect and determine the distance to objects. Doppler radar systems can determine the speed of a car or the intensity of a rainstorm. Radar is used to map the Earth and other planets.
Step-by-step explanation:
Radar is a common application of microwaves that was first developed in World War II. By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds and aircraft. A Doppler shift in the radar echo can be used to determine the speed of a car or the intensity of a rainstorm. Sophisticated radar systems are used to map the Earth and other planets, with a resolution limited by wavelength. The shorter the wavelength of any probe, the smaller the detail it is possible to observe.