Radio uses radio waves to transmit information by modulating properties of electromagnetic waves like amplitude, frequency, and phase. Radio waves are a type of electromagnetic radiation with wavelengths longer than infrared light. A transmitter generates radio frequency alternating current to produce radio waves, while a radio receiver receives radio waves and converts the information to a usable form using an antenna. Frequency refers to the number of cycles per second in alternating current, and the electromagnetic spectrum includes all known frequencies and wavelengths of photons.