In addition to conventional cameras, which use visible light, satellites transmit images that are generated by heat, electromagnetic radiation, and sound. Commercial uses of infrared sensors include sinks that turn on automatically and toilets that flush automatically. Some burglar alarms are triggered by sensing the heat from intruding bodies. Thermal scans surveying homes for energy efficiency reveal where there are heat leaks. Heat-sensing night goggles were used by the military in Desert Storm to identify enemy targets.
Radar uses radio waves to measure the time it takes to send and receive electromagnetic radiation.
Unlike TV cameras, radar can be used at night and on cloudy days. Air traffic control is perhaps the most important use of radar, ensuring that planes approaching an airport don't collide with each other. Radar guns are used in law enforcement for calculating the speed of a vehicle and in baseball to measure the speed of a pitch. Sonar uses sound waves operating best through the dense medium of water. Submarines use sonar to find their way under water, imitating the natural sonar of dolphins and bats.