Radio Waves
Radio waves are a type of electromagnetic radiation. A radio wave has a much longer wavelength than visible light. Humans use radio waves extensively for communications.
Radio Waves
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, X-rays, and gamma-rays.
Radio waves have the longest wavelengths in the EM spectrum, according to NASA, ranging from about 1 millimeter to more than 100 kilometers.
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 to create electromagnetic waves.
Hertz became the first person to transmit and receive controlled radio waves. The unit of frequency of an EM wave is called a hertz, in his honor, according to the American Association for the Advancement of Science.
Frequencies
Shortwave radio uses frequencies in the HF band, from about 1.7 megahertz to 30 megahertz, according to the National Association of Short-wave Broadcasters (NASB). Within that range, the shortwave spectrum is divided into several segments, some of which are dedicated to regular broadcasting stations, such as the Voice of America, the British Broadcasting Corp. and the Voice of Russia.
Throughout the world, there are hundreds of shortwave stations, according to the NASB. Shortwave stations can be heard for thousands of miles because the signals bounce off the ionosphere, and rebound back hundreds or thousands of miles from their point of origin.