What Are Radio Waves?

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A radio tuner receives radio waves and converts them to mechanical vibrations in the speaker to create sound waves that can be heard.
Credit: Ensuper | Shutterstock
▼ Radio waves are a type of electromagnetic radiation best-known for their use in communication technologies, such as television, mobile phones and radios. These devices receive radio waves and convert them to mechanical vibrations in the speaker to create sound waves.
The radio-frequency spectrum is a relatively small part of the electromagnetic (EM)  spectrum. The EM spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency, according to the University of  Rochester. The common designations are radio waves, microwaves, infrared(IR), visible light, ultraviolet(UV), X-raysand gamma-rays.
Radio waves have the longest wavelengths in the EM spectrum, according to NASA, ranging from about 0.04 inches (1 millimeter) to more than 62 miles (100 kilometers). They also have the lowest frequencies, from about 3,000 cycles per second, or 3 kilohertz, up to about 300 billion hertz, or 300 gigahertz.
The radio spectrum is a limited resource and is often compared to farmland. Just as farmers must organize their land to achieve the best harvest regarding quantity and variety, the radio spectrum must be split among users in the most efficient way, according to the British Broadcasting Corp.  (BBC). In the U.S., the National Telecommunications and Information Administration within the United States Department of Commerce manages the frequency allocations along the radio spectrum.
Discovery
Scottish physicist James Clerk Maxwell, who developed a unified theory of electromagnetism in the 1870s, predicted the existence of radio waves, according to the National Library of Scotland. In 1886, Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. Hertz used simple homemade tools, including an induction coil and a Leyden jar (an early type of capacitor consisting of a glass jar with foil layers both inside and out) to create electromagnetic waves. Hertz became the first person to transmit and receive controlled radio waves. The unit of frequency of an EM wave — one cycle per second — is called a hertz, in his honor, according to the American Association  for the Advancement of Science.
Bands of radio waves
The National Telecommunications and  Information Administrationgenerally divides the radio spectrum into nine bands: (▪ ▪ ▪)

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