Radio waves are a type of electromagnetic radiation with wavelengths ranging from 300 GHz to 3 kHz. They transmit information over long distances using transmitters and antennas. Radio waves can travel via ground waves or direct waves and are used for radio, television, and communication technologies like WiFi. Television transmits moving images and sound using electromagnetic signals and has been an important source of entertainment and information since the 1920s. Microwaves have short wavelengths measured in centimeters and can penetrate some materials, making them useful for radar, wireless networks, and cooking.