Radio wave facts for kids

Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (−). Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves. The action is drastically slowed down in this animation.

Radio waves are a type of energy that moves through the air, like the waves you see in the ocean, but you can't see them! They are used to send all sorts of information, from music on the radio to messages to astronauts in space. Let's dive in and learn more about these amazing waves!

What are they?

Radio waves are a type of electromagnetic radiation. That's a big term, but it just means they are a form of energy that travels in waves and has both electrical and magnetic properties. Radio waves have the lowest frequencies and the longest wavelengths in the electromagnetic spectrum. Think of the electromagnetic spectrum as a giant ruler that measures all types of electromagnetic radiation, from very short waves like gamma rays to very long waves like radio waves.

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

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

How fast do radio waves travel?

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

Where do radio waves come from?

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

1. Naturally: Lightning and objects in space, like stars and galaxies, can produce radio waves. Everything that is warm emits radio waves as well.
2. Artificially: We can create radio waves using a device called a transmitter. The transmitter is connected to an antenna, which sends the radio waves out into the world.

How do we use radio waves?

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

• Radio Communication: This is how we send voices and music through the air to radios in cars and homes.
• Broadcasting: Radio and television stations use radio waves to send their programs to your TV or radio.
• Radar: Radar systems use radio waves to detect objects, like airplanes or ships, and to measure their speed and distance.
• Navigation Systems: Systems like GPS use radio waves from satellites to help you figure out where you are on Earth.
• Communication Satellites: Satellites use radio waves to send signals back and forth to Earth, allowing us to make phone calls and watch TV from anywhere in the world.
• Wireless Computer Networks: Wi-Fi uses radio waves to connect your computer or phone to the internet without wires.

How do 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 obstacles like mountains and follow the curve of the Earth. This is how 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 called the ionosphere and 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 that different users don't interfere with each other. An international organization called the International Telecommunication Union (ITU) helps to keep everything organized. They divide the radio spectrum into different bands, each with its own frequency range, and assign these bands to different uses. This helps to prevent chaos and ensures that everyone can use radio waves without causing problems for others.

Discovery

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

In 1887, a German physicist named Heinrich Hertz proved that Maxwell's theory was correct. He built a machine that could create and detect radio waves. He showed that radio waves had the same properties as light, like the ability to be reflected, refracted, and polarized.

An Italian inventor named Guglielmo Marconi developed the first practical radio transmitters and receivers in the late 1890s. He was able to send and receive radio signals over long distances, and he is considered the father of radio. In 1909, Marconi won the Nobel Prize in Physics for his 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, which then radiates the energy as radio waves.

Radio waves are received by another antenna connected to a radio receiver. When radio waves hit the receiving antenna, they cause the electrons in the metal to move back and forth, creating a tiny electrical current. The receiver detects this current and turns it into a signal that we can hear or see.

Radio waves as particles

In addition to thinking of radio waves as waves, we can also think of them as tiny particles called photons. Photons are tiny packets of energy that 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 an enormous number of photons every second.

Properties of radio waves

• Speed: Radio waves travel at the speed of light in a vacuum.
• Wavelength and Frequency: The wavelength and frequency of a radio wave are related. The higher the frequency, the shorter the wavelength, and vice versa.
• Polarization: Radio waves have a property called polarization, which describes the direction of the wave's electric field. Radio waves can be horizontally polarized, vertically polarized, or circularly polarized.

How radio waves travel

Radio waves can travel in different ways depending on their frequency and the environment:

• Line of Sight: Radio waves travel in a straight line from the transmitter to the receiver. This is the most common way for radio waves to travel over short distances.
• Diffraction: Radio waves can bend around obstacles, like buildings or hills. This allows radio waves to travel beyond the horizon.
• Reflection: Radio waves can bounce off surfaces, like the ground or the ionosphere. This allows radio waves to travel very long distances.

Radio communication systems

Radio communication systems use radio waves to send information from one place to another. These systems consist of a transmitter, an antenna, a receiver, and another antenna.

The transmitter takes the information that needs to be sent, such as a voice or a picture, and converts it into an electrical signal. The transmitter then uses this signal to modulate a radio wave. Modulation is the process of changing some property of the radio wave, such as its frequency or amplitude, to encode the information.

The modulated radio wave is then sent to the transmitting antenna, which radiates the radio wave into the air. The radio wave travels through the air to the receiving antenna, which picks up the radio wave.

The receiver then demodulates the radio wave to extract the information that was encoded on it. The receiver then converts this information back into a form that can be understood, such as a voice or a picture.

Effects on living things and the environment

Radio waves are a type of non-ionizing radiation. This means that 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 exposure to 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 is difficult to get a cell phone signal inside a metal building.

Measuring

Radio waves have both an electric and a magnetic component, so we can measure their intensity using units specific to each component.

• Electric Component: Measured in volts per meter (V/m).
• Magnetic Component: Measured in amperes per meter (A/m).

Another way to measure radio waves is by power density, which is the amount of power per unit area. Power density is measured in milliwatts per square centimeter (mW/cm²).

See also

In Spanish: Ondas de radio para niños