radio wave: Quick Facts

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Oct. 14, 2026

Did You Know?

Radio waves have the longest wavelengths out of all known waves in the electromagnetic spectrum, and can range from the length of a football to more than the diameter of Earth.
The Very Large Array (VLA) is a radio telescope in the U.S. state of New Mexico, and is comprised of 27 antennas arranged in a Y-shape stretching approximately 22.4 mi (36 km) wide, 1.5 times the width of Washington, D.C., United States.
A radio works by converting a specific wavelength (which can be adjusted by the user by changing the station) into vibrations, generating sound from the speakers.
If an object is not a receiver for radio waves, any approaching wave will simply bounce off that object and travel away.

Photos and Videos

Figure 1: The electromagnetic spectrum.

Schematic diagram showing the propagation of high-frequency (shortwave) radio waves by reflection off the ionosphereSpecific ionization conditions vary greatly between day (left) and night (right), causing radio waves to reflect off different layers of the ionosphere or transmit through them, depending upon their frequency and their angle of transmission. Under certain conditions of location, ionization, frequency, and angle, multiple “skips,” or reflections between ionosphere and Earth, are possible. At night, with no intervening layers of the ionosphere present, reflection off the F layer can yield extremely long transmission ranges.

Diagram showing how radio waves travel beyond the horizon: one path follows the Earth's surface as a ground wave, while another, the sky wave, bounces off the ionosphere and returns to Earth.

Diagram of the electromagnetic spectrum with labeled sections for radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, each paired with an example use and corresponding image.

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Topics

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electromagnetic radiation: Radio waves

Key People

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Vitaly Ginzburg

Russian physicist

Sir Oliver Joseph Lodge.

Sir Oliver Joseph Lodge

British physicist

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George Francis FitzGerald

Irish physicist

Heinrich Hertz

Heinrich Hertz

German physicist

Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.

Physics and Natural Law