Have you ever gone on a road trip and lost your favorite radio channel as you left the city? Whether you knew it or not, the static from your radio came from a disruption in radio waves.
From the song that gets you grooving to the internet you surf on your phone, radio waves influence how we communicate.
Let’s get into everything you need to know about radio waves below!
Radio Waves: A Complete Explanation
Radio waves make up the first part of the electromagnetic spectrum. They have the longest wavelength and lowest power among all the radiation types. Radio waves also make up the largest section of the spectrum, with frequencies ranging from the size of a grain of rice to beyond the radius of the Earth.
Similar to other short portions of the spectrum such as infrared, scientists usually measure radio waves in frequency, measured in Hertz, and wavelength, which is measured in meters.
While there isn’t a definitive line for where radio waves start and stop, they typically measure from 300GHz (or about 1cm) to over 3KHz (or 100km). The higher frequency range of radio waves often includes microwaves.
Because of their incredible frequency range, radio waves interact uniquely with the Earth’s ionosphere. This is a layer of the atmosphere that absorbs ultraviolet radiation, causing it to activate and reflect this low-frequency radiation. Depending on the frequency, radio waves transmitted from Earth’s surface can bounce from receiver to receiver (excluding a specific portion of mid-band waves).
Due to their ability to bounce below the ionosphere, radio waves make up the foundation of our communication systems. Their more practical uses include AM and FM transmissions and cell phones. However, their specific frequencies that penetrate the atmosphere make them useful for communicating by orbital satellites.
Radio waves come naturally from objects that have the potential to create electric currents. While we see them emitted naturally from lightning and some celestial bodies, their discovery in the late 1800s showed us how to create them artificially using electric currents. While not dangerous, researchers have speculated on their impact on the human brain.
Radio Waves: the Exact Definition
NASA defines radio waves as “electromagnetic radiation which has the longest wavelength, the lowest frequency, and is produced by charged particles moving back and forth.”
The radio wave portion is one of the most comprehensive sections of the electromagnetic spectrum. The National Telecommunications and Information Administration (NTIA) breaks up this radio frequency spectrum into 8 bands, which we outline below.
|Radio Wave Section||Frequency (measured in Hertz)|
|Extremely Low Frequency (ELF)||< 3kHz|
|Very Low Frequency (VLF)||3 – 30kHz|
|Low Frequency (LF)||30 – 300kHz|
|Medium Frequency (MF)||300kHz – 3MHz|
|High Frequency (HF)||3 – 30MHz|
|Very High Frequency (VHF)||30 – 300MHz|
|Ultra High Frequency (UHF)||300MHz – 3GHz|
|Super High Frequency (SHF)||3 – 30GHz|
Where Do Radio Waves Come From?
Radio frequencies in space come from a collision of magnetic fields between large objects. The sun is the largest source of radio waves in our solar system, which can dominate the longest wavelengths during geomagnetic storms.
Jupiter, the second largest object in our solar system, also emits a significant amount of radio waves when reflecting off its moons. Both Io and Ganymede manipulate the gas within Jupiter’s magnetosphere, causing massive electric currents.
How are Radio Waves Created?
Researchers use antennas, which control the path of charged electrons within a conductor, to emit low-frequency radiation. The antenna receives an electric current that vibrates back and forth, causing the equipment to radiate power. The antenna transmits its electromagnetic radiation to a second antenna, which directs it to a receiver.
Who Discovered Radio Waves?
In 1862, Scottish mathematician James Clerk Maxwell made groundbreaking discoveries while working with prominent equations in electricity and magnetism.
Using Ampere’s corrected Circuital Law, Maxwell discovered an electromagnetic wave equation that strongly correlated with the speed of light. The mathematician concluded that light and magnetism were the results of the same cause, and that light consisted of electromagnetic waves. He titled his discovery A Dynamical Theory of the Electromagnetic Field.
25 years later, German physicist Heinrich Hertz brought Maxwell’s theory to life with experimentation. Hertz’s experiment involved an induction coil and an improvised capacitor to create electromagnetic waves. He used two electrodes separated by a gap to detect the waves. Although they were incredibly small, Hertz witnessed the waves as they passed through the spark gap. The physicist determined that these waves included all of the properties that Maxwell laid out in his equations.
What are the Applications of Radio Waves?
Radio stations use low and medium-frequency radio waves to transmit sounds to people across states and regions. AM radio uses energy that ranges from 535kHz to 1.7MHz.
FM radio uses a frequency nearly 100 times faster, which results in a clearer sound while sacrificing range.
When you make a phone call, you’re transmitting radio waves. Your cell phone works as a transmitter that sends radio waves at an ultra-high frequency to receivers around the world.
The higher the frequency of your phone, the further its radio wave travels before the ionosphere reflects it back to earth.
Scientists use radio telescopes to observe celestial objects that emit low-frequency energy. These typically come in as large energetic regions, such as pulsars and space clouds, rather than points of light, such as stars. Radio telescopes are excellent at studying quasars, which are supermassive black holes that power the center of some galaxies.
Examples of Radio Waves in the Real World
The spaceflight company, SpaceX, is working to connect the world to satellite internet with its project constellation, Starlink. The 42,000 satellite constellation uses 12GHz waves to transmit data down to Earth. While this mid-band wave is typically reserved for satellite communication, Dish Network plans on using it to connect people via 5G cell towers.
Communications companies such as Verizon and T-Mobile use high-frequency radio waves to transmit large amounts of data from under the ionosphere. 5G wavelengths range from about 30 to 300GHz, with higher download speeds correlating with higher frequencies.
However, fluctuations in the atmosphere can cause disruptions in service, and companies are experimenting with lower frequencies to facilitate.
National Radio Astronomy Observatory
Astronomers in New Mexico use the Very Large Array (VLA) radio telescope to collect radio images at a higher resolution than any other observatory in the world. The VLA uses 27 antennas measuring 82 feet in diameter to collectively analyze spacial radio waves. The antennas, which span across 22 miles, receive super-high frequency waves ranging from 1GHz to 50GHz.
Radio Waves: Further Reading
From unlimited data to galactic quasars, we use radio waves in a variety of applications. These low frequencies make up a portion of the entire electromagnetic spectrum. For more on how we use this technology in our society, check out the articles below.
- What are EMFs (Electric and Magnetic Fields)? Are They Safe?
- Bluetooth vs. Infrared: What’s the Difference?
- Top 10 Largest Space Telescopes in Orbit
Starlink vs. 5G: Which is Better?
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