Radio wave facts for kids

This animation shows a half-wave dipole antenna sending out radio waves. The antenna is made of two metal rods. An alternating current from a radio transmitter (not shown) makes the rods charge positive (+) and negative (−) in turns. Loops of electric field (black lines) leave the antenna and travel away at the speed of light. These loops are the radio waves. The animation is much slower than real life!

Radio waves are a type of energy that travels through the air, like invisible waves in the ocean. You can't see them, but they are all around us! We use them to send many kinds of information. This includes music on the radio, signals for your cell phone, and even messages to astronauts in space. Let's learn more about these amazing waves!

What Are Radio Waves?

Radio waves are a form of electromagnetic radiation. This means they are a type of energy that travels in waves. They have both electrical and magnetic parts. Radio waves have the lowest frequencies and the longest wavelengths in the electromagnetic spectrum. Think of the electromagnetic spectrum as a giant ruler. It measures all types of energy waves, from tiny gamma rays to very long radio waves.

Understanding Frequency and Wavelength

• Frequency: This is how many wave peaks pass a certain point in one second. It is measured in Hertz (Hz). Radio waves have frequencies below 300 gigahertz (GHz). A gigahertz is a billion Hertz!
• Wavelength: This is the distance between two wave peaks. Radio waves have wavelengths longer than 1 millimeter (about the size of a grain of rice).

Radio waves with frequencies above 1 GHz and wavelengths shorter than 30 centimeters (about the length of a ruler) are called microwaves. Microwaves are used in ovens to heat food. They also help cell phones send signals.

How Fast Do Radio Waves Travel?

Radio waves are super speedy travelers! In empty space, they zoom along at the speed of light. This is about 299,792,458 meters per second. That's incredibly fast! When radio waves travel through the air, they slow down just a tiny bit.

Where Do Radio Waves Come From?

Radio waves are made when tiny charged particles, like electrons, move back and forth. This can happen in two main ways:

• Naturally: Lightning and objects in space, like stars and galaxies, create radio waves. Everything that is warm also gives off some radio waves.
• Artificially: We can make radio waves using a device called a radio transmitter. The transmitter is connected to an antenna. The antenna then sends the radio waves out into the world.

How Do We Use Radio Waves?

Radio waves are used in many important ways in our modern world:

• Radio Communication: This is how we send voices and music through the air. Your car radio or home radio picks up these signals.
• Broadcasting: Radio and television stations use radio waves. They send their programs to your TV or radio.
• Radar: Radar systems use radio waves to find objects. They can detect airplanes or ships. They also measure how fast and far away these objects are.
• Navigation Systems: Systems like GPS use radio waves from satellites. These waves help you figure out where you are on Earth.
• Communication Satellites: Satellites use radio waves to send signals to and from Earth. This lets us make phone calls and watch TV from almost anywhere.
• Wireless Computer Networks: Wi-Fi uses radio waves. It connects your computer or phone to the internet without wires.

How Radio Waves Travel

Radio waves don't always travel in a straight line. They can travel in different ways depending on their frequency:

• Ground Waves: Long radio waves can bend around things like mountains. They can also follow the curve of the Earth. This is how some radio stations can reach you even if you are far away.
• Skywaves: Shorter radio waves can bounce off a layer in the Earth's atmosphere. This layer is called the ionosphere. After bouncing, they travel back to Earth. This allows radio waves to travel very long distances.
• Line of Sight: Very short radio waves travel in a straight line. This means they can only travel as far as you can see. This is how cell phones and Wi-Fi work.

Keeping Radio Waves Organized

Because radio waves are so useful, it's important to make sure different users don't interfere with each other. An international group called the International Telecommunication Union (ITU) helps keep everything organized. They divide the radio spectrum into different bands. Each band has its own frequency range. These bands are given to different uses. This helps prevent problems and makes sure everyone can use radio waves without causing trouble for others.

Discovery of Radio Waves

The idea of radio waves was first suggested by a scientist named James Clerk Maxwell in 1867. He created a set of equations, now called Maxwell's equations. These equations predicted that electric and magnetic fields could travel through space as electromagnetic waves. Maxwell also thought that light was a type of electromagnetic wave.

In 1887, a German physicist named Heinrich Hertz proved Maxwell's idea was right. He built a machine that could create and detect radio waves. He showed that radio waves acted like light. They could be reflected, refracted, and polarized.

An Italian inventor named Guglielmo Marconi then developed the first useful radio transmitters and receivers. This happened in the late 1890s. He was able to send and receive radio signals over long distances. Marconi is often called the father of radio. In 1909, he won the Nobel Prize in Physics for his important work.

How Radio Waves Are Made and Received

Radio waves are made when electrons move back and forth in a special metal object called an antenna. A device called a radio transmitter sends an electrical current to the antenna. The antenna then sends out this energy as radio waves.

Radio waves are picked up by another antenna. This antenna is connected to a radio receiver. When radio waves hit the receiving antenna, they make the electrons inside it move back and forth. This creates a tiny electrical current. The receiver detects this current. It then turns it into a signal that we can hear or see.

Radio Waves as Particles

Besides thinking of radio waves as waves, we can also think of them as tiny particles. These particles are called photons. Photons are tiny packets of energy. They make up all electromagnetic radiation, including light and radio waves.

The energy of a single radio photon is very small. However, even a low-power transmitter sends out a huge number of photons every second.

Properties of Radio Waves

• Speed: Radio waves travel at the speed of light in a vacuum (empty space).
• Wavelength and Frequency: The wavelength and frequency of a radio wave are connected. If the frequency is higher, the wavelength is shorter. If the frequency is lower, the wavelength is longer.
• Polarization: Radio waves have a property called polarization. This describes the direction of the wave's electric field. Radio waves can be horizontally polarized, vertically polarized, or circularly polarized.

Effects on Living Things

Radio waves are a type of non-ionizing radiation. This means they do not have enough energy to damage cells or DNA. The main effect of radio waves on living things is to heat them up. This is how microwave ovens cook food.

There has been some concern about the possible health effects of radio waves from cell phones and other devices. However, most studies have not found any evidence that radio waves cause cancer or other health problems.

Radio waves can be blocked by metal objects. This is why it can be hard to get a cell phone signal inside a metal building.

See also

In Spanish: Ondas de radio para niños