Radio waves

Discovery and use of radio waves

By Robert M. Hazen, Ph.D., George Mason University

There are a bunch of common divisions in this electromagnetic spectrum. They are radio waves; microwave; infrared or thermal radiation; then visible light; then ultraviolet; radiography; and gamma rays. This list is in order of increasing energy, also decreasing wavelengths. But one of the most important types of waves that is widely used by humans is radio waves. But what are radio waves and how are they used?

Communication of the city by radio waves.
Radio waves are used for all types of human communication. (Image: metamorworks / Shutterstock)

The electromagnetic spectrum

The electromagnetic spectrum is the continuum of all possible wavelengths, or equivalently all possible frequencies of electromagnetic radiation. There are no natural sharp divisions in this spectrum. Every possible wavelength, every possible frequency can be produced. And there are really no natural divisions except from the human point of view that we see visible light and we don’t see others.

But intrinsically, they’re all the same kind of phenomenon: all electromagnetic radiation, all moving at 186,000 miles per second. Radio waves were the very first type of invisible electromagnetic radiation to be discovered. They illustrated the behavior of electromagnetic radiation.

This is a transcript of the video series The joy of science. Watch it now, on Wondrium.

The discovery of radio waves by Hertz

Radio waves were first discovered by German physicist Heinrich Rudolph Hertz, and it was in a series of experiments in the late 1880s.

Hertz read James Maxwell’s papers. He was determined to observe these predicted invisible types of radiation. He set up a series of experiments to do just that. And he was able to measure the wavelengths and some of the other characteristics of these invisible waves.

By the way, the unit of frequency is called hertz. One hertz is one cycle per second, and it is named in its honor. So when you look at the dial on your radio, you may see kilohertz or megahertz; which bears the name of this great German scientist.

Learn more about the electromagnetic spectrum.

Marconi and radio communication

Shortly after Hertz’s research, the practical use of radio communication was demonstrated by the Italian inventor Guglielmo Marconi. It generated radio waves with a primitive spark device – only making electric sparks – and these created radio waves. And then he used a telegraph to make short bursts like this.

A portrait of Guglielmo Marconi.
Marconi was the first to concretely demonstrate the use of radio waves for communication. (Image: Pach Brothers / Public domain)

Much of his success is due to the fact that he designed and improved antennas. He was the first, for example, to take an antenna, put it in a vertical configuration, and ground it so that you had much better receiving characteristics. Gradually, he was able to increase the transmission and reception of these radio waves from one mile to ten miles, finally to 100 miles in 1896.

And they were just short bursts of radio pulses, like Morse code. Marconi established the first transatlantic wireless communication in 1908 and won the Nobel Prize in Physics in 1909.

Radio waves are on the spectrum

Radio waves include electromagnetic radiation with wavelengths ranging from about a foot to several kilometers in length, the most energetic part of the electromagnetic spectrum, the longest wavelengths. The frequency of these waves is measured in thousands or millions of cycles per second, that is to say in kilohertz or in megahertz.

Radio waves, like all electromagnetic waves, are produced when charged particles move back and forth and oscillate. The tall antennas you see near many radio stations are metallic structures in which large numbers of electrons swing back and forth, producing the strong radio signals you detect.

Radio waves are ideal for communication because they travel through the atmosphere. They travel through building materials. Shorter wavelength radios, such as what we call FM broadcast waves, are not easily dispersed. They require some sort of line of sight to the radio tower, so normally you can’t get an FM radio station more than 40 or 50 miles from its source.

Amplitude and frequency modulation

But under the right conditions, longer wavelengths, AM radio broadcasts, can actually bend, bounce off the atmosphere, disperse and therefore travel several hundred kilometers, even beyond the air. horizon.

Information is generally conveyed by a radio signal in two different ways. You can change the amplitude of the wave, where you change the intensity of the wave. But you can also use frequency modulation, or FM broadcast, and it’s nothing more than changing the wavelength of the wave slightly. It is analogous to an FM or frequency modulated broadcast.

Learn more about the nature of energy.

Radio band divisions

A portable radio station.
Different radio frequencies are used for different types of communication. (Image: polar isatis / Shutterstock)

Because radio waves radiate in so many different directions and over such great distances, society must regulate who uses which wavelength, or which radio band, so to speak.

That’s why we have the International Telecommunication Union, it’s a United Nations agency; and also in the United States, the Federal Communication Commission is the FCC. These control what is called electromagnetic real estate, because each wavelength is some kind of valuable asset that you can transmit information about.

Specific radio bands are allocated, for example, to amateur radio operators, police, emergency vehicles, navigation, space communications — very important to have a separate band for this — and so on.

Also, there are a few specific wavelengths that have been set aside as standard frequencies, and they broadcast on that frequency all the time. And you can use your radio receivers to pick up those specific frequencies and make sure your equipment is working properly.

Radio astronomy

Radio astronomers use large dish-shaped antennas to detect radio waves from distant objects: stars and galaxies far away. These stars and galaxies have swirling clouds of charged particles, and so many objects in space emit radio waves as they accelerate charged particles.

These waves travel 186,000 miles per second in space, sometimes for hundreds of millions of years, and are picked up by radio telescopes. You can also use radio waves as a means of possibly detecting the existence of intelligent life elsewhere in the universe, because if you wanted to communicate from planet to star to star, this is how you would.

Radio waves are therefore one of the most important forms of electromagnetic radiation which is an integral part of human technology, especially communication.

Common questions about radio waves

Q: Who discovered radio waves?

Radio waves were discovered by German physicist Heinrich Rudolph hertz, and it was in a series of experiments in the late 1880s.

Q: How has radio communication been concretely demonstrated?

The practical use of radio communication was demonstrated by the Italian inventor Guglielmo Marconi. It generated radio waves with a primitive spark device – only making electric sparks – and these created radio waves. And then he used a telegraph to make short bursts like this.

Q: Why are radio waves ideal for communication?

Radio waves are ideal for communication as they travel through the atmosphere. They travel through building materials. Shorter wavelength radios, such as what we call FM broadcast waves, are not easily dispersed.

Q: How are radio bands allocated?

Specific radio bands are allocated, for example, to radio amateurs, police, emergency vehicles, navigation, space communications — very important to have a separate band for that — and so on. Also, there are a few specific wavelengths that have been set aside as standard frequencies, and they broadcast on that frequency all the time.

Keep reading
From radio to television: the history of electronic communication
Who invented radio astronomy? A history of the radio telescope
Radio Hiss, Einstein’s theory of relativity and the universe