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The Seven Types of Electromagnetic Waves

Nicholas Amendolare, Maria Howard
  • Author
    Nicholas Amendolare

    Nicholas Amendolare is a high school and middle school science teacher from Plymouth, Massachusetts. He has a bachelor's degree in environmental science from Worcester Polytechnic Institute and a master's degree in education from Harvard University. He has been a teacher for nine years, has written for TED-Ed, and is the founder of www.MrAscience.com.

  • Instructor
    Maria Howard

    Maria is a teacher and a learning specialist and has master's degrees in literature and education.

Discover the different types of electromagnetic waves and what defines an electromagnetic wave. Understand the term electromagnetic and see an electromagnetic wave diagram. Updated: 11/03/2021

Electromagnetic Waves Definition

Electromagnetic waves are simultaneous periodic oscillations in the intensity of an electromagnetic field. Unlike traditional waves, they do not need a medium to travel through, and they travel at the speed of light. There are seven types of electromagnetic waves: radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.

What does Electromagnetic Mean?

The term "electromagnetic" simply means "related to electromagnetism." Electromagnetism refers to the two overlapping worlds of magnetism and electricity in the scientific context. Although electricity and magnetism were discovered independently, electromagnetism is now considered the fundamental physical force that explains reactions between charged particles (protons and electrons) and the release of photons (electromagnetic waves).

The first scientist to bridge the gap between electricity and magnetism was Gian Romagnosi. In 1802, he discovered that running an electric current through a battery would disturb a nearby compass needle. But it wasn't until James Clerk Maxwell, a few decades later, that electricity and magnetism were unified in a single theory. The worlds of magnetism, charged particles, protons, electrons, and electricity were finally brought together.

However, Maxwell's theories were not compatible with classical mechanics, including Newton's laws. And it wasn't until Albert Einstein's 1905 paper on special relativity that this incompatibility was fully explained. Today, we consider electricity (the flow of electrons) and magnetism (the interactions between protons, electrons, and light) to be two sides of the same coin.

Terms related to Electromagnetic Waves

There are many terms related to electromagnetism, most of which have origins in the physics of physical waves, as one might find in the ocean. The following is a brief definition of six very important terms related to the structure of waves.

  • Wavelength: Wavelength is the length of a wave, measured from crest to crest or from trough to trough. The wavelength of visible light is very small, only a few hundred nanometers.
  • Frequency: Frequency is the number of cycles that a wave experiences per unit time. Typically, frequency is measured in Hertz (cycles per second).
  • Amplitude: Amplitude is the height of a wave, measured from the middle of a wave up to the height of its crest. However, the amplitude of electromagnetic waves is a matter of intensity rather than physical height and is measured using units like volts and amps.
  • Crest: A crest is the high point in a wave. In a physical wave, this refers to maximum height. In an electromagnetic wave, this refers to maximum intensity.
  • Trough: A trough is the low point in a wave (the exact opposite of the crest). In a physical wave, this refers to the minimum height. In an electromagnetic wave, this refers to minimum intensity.
  • Cycle: A cycle is one full oscillation of a wave, from the time one crest arrives to the time a second crest arrives.

Heinrich Hertz and Electromagnetic Waves

Who is Heinrich Hertz? If you guessed that he was the founder of the popular American car rental company with a similar name, you're not alone. But Heinrich Hertz wasn't a car rental entrepreneur. Instead, he was a German scientist who performed experiments with electricity when electricity was still a fancy new thing that scientists had a lot to learn about.

In 1888, when Hertz was 30, he made an electric spark jump from one terminal to another and noticed a second spark at the same time between two terminals a couple of yards away. Exciting stuff, I know, but this was 1888, and what Hertz noticed was a different kind of electromagnetic wave that eventually came to be known as Hertzian waves.

A few years later, in 1896, a young Italian scientist named Guglielmo Marconi built on Hertz's discovery and created the first radio transmitter, sending radio signals for a mile. (A mile!) Hertzian waves are now called radio waves and are used every day, from listening to the radio to watching TV.

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Electromagnetic Wave Diagram

Electromagnetic waves are not invisible. Our eyes can detect them, of course. Visible light is simply one of the seven types of electromagnetic waves, the type our eyeballs can detect. Across the electromagnetic spectrum there are six other types as well. But unlike with physical waves that one might find in a pond or in the ocean, the structure of electromagnetic waves in invisible. To help imagine the shape of such waves, scientists use diagrams like the one below.

A diagram of an electromagnetic wave.

A diagram of an electromagnetic wave.

Electromagnetic waves can be visualized as pictured, with a simultaneous oscillation of the strength of both the electric and the magnetic fields. Thus, the two waves shown can be thought of as one wave with both a vertical component (electric) and horizontal component (magnetic).

The frequency of the wave would be a measure of how many times it completes a cycle in each second. The frequency of electromagnetic waves is very high, completing millions upon millions of cycles each second. The wavelength of the wave could be measured by taking a ruler (in this case, a very tiny ruler) and measuring the waves from crest to crest or trough to trough. The wavelength of electromagnetic waves are tiny, usually measured in nanometers. Finally, by measuring the frequency and wavelength, we could determine where this wave falls in the electromagnetic spectrum. It could be visible light, or a radio wave, or even an X-ray, depending on its wavelength and frequency. For more information on the types of electromagnetic waves, read the section below.

Types of Electromagnetic Waves

There are seven types of electromagnetic waves, all of which are similar periodic oscillations in the electromagnetic field. Scientists simply classify the waves based on their frequency and wavelength (which go hand in hand). Put together, one ends up with a diagram of the entire electromagnetic spectrum, as can be seen in the image.

A diagram of the electromagnetic spectrum.

A diagram of the electromagnetic spectrum

The seven types of electromagnetic waves can be thought of as seven different kinds of light. There is only one kind that our eyeballs can detect. However, it is important to note that this is a very human distinction. Some snakes can see infrared light. Some birds can detect ultraviolet light. All in all, these seven types of waves are fundamentally the same. The only difference is their frequency and, ultimately, their effects.

What are Electromagnetic Waves?

We are surrounded by waves we can see and hear, from ocean waves to sound waves. A wave shows the transfer of energy, from the wind that starts an ocean wave to the sound that moves through the air to your ear drum. Waves that pass through a physical object or medium are called mechanical waves. Unlike mechanical waves, electromagnetic waves do not need a medium to travel or propagate. Electric and magnetic fields both produce vibrations and, together, the two types of energy create electromagnetic waves.

Waves take different shapes, but electromagnetic waves all have a snake-like shape which makes them transverse waves. Transverse waves are measured by their height, or amplitude, and by their wavelength, or the distance between the highest point of one wave, the crest, to the crest of the next wave. The lowest point of a wave is called a trough. Trough to trough can be measured, too. When analyzing an electromagnetic wave, both the amplitude and distance between waves is measured.

We measure both the amplitude, or height of a wave (a), and the distance between waves (b).
Diagram of a wavelength

One whole wave, from crest to crest, or trough to trough, is called a cycle. The number of cycles that occur per second is the wave's frequency. In honor of Heinrich Hertz, we measure frequency in hertz or Hz.

Types of Electromagnetic Waves

Electromagnetic waves are ordered on the electromagnetic spectrum by frequency. They range from radio waves with fewer cycles per second to the extraordinarily fast and harmful high frequency of gamma rays.

Radio waves have the lowest frequency of the seven bands of waves on the electromagnetic spectrum, which also means they have the least amount of energy. Radio waves have wavelengths measuring from miles to the length of a football, or around 11 inches.

It is common to talk about the frequency of radio waves, or the number of waves per second. When tuning in to a radio station, a person is listening to a specific frequency of radio waves. AM stations are numbered from 520 to 1610, with each number representing the frequency of the station at thousands of hertz per second, or kilohertz, abbreviated kHz. FM station frequencies range from 87.0 to 107.9 million hertz per second, called megahertz or MHz.

Sound is converted into EM waves and sent through radio dishes like this one. Your radio then receives these radio waves and changes them back into sound waves.
Image of a radio satellite

Next on the spectrum are microwaves, a type of radio wave that are less than 11.8 inches long. The microwaves people use to heat food have waves measuring about five inches. Microwaves aren't just for heating leftovers or cups of coffee, though. Microwaves are also used for radar, television and satellites.

Microwaves occur at higher frequencies, with billions or even trillions of cycles occurring per second. Since writing out 4,000,000 hertz is kind of clunky, it would be written as 4 gigahertz or 4 GHz. Digital radio is broadcast at a frequency of 2.5 billion hertz per second, or 2.5 GHz.

Infrared waves occur at an even higher frequency than microwaves. Infrared waves are used to power television remote controls and for thermal imaging, like when using a pair of night vision goggles. When you feel warmed by the sunlight, the energy you feel is infrared radiation from the sun. Since infrared waves have such high frequencies, their wavelengths are so tiny they are only hundredths or thousandths of an inch.

All electromagnetic waves are light, but the band of the electromagnetic spectrum that people and animals can see is called visible light. When a beam of light passes through a prism, a person can see each color of the rainbow separated into their individual wavelengths. Red, the longest of the wavelengths, measures around 700 nanometers; yellow is around 600 nanometers; and violet, the shortest, is around 400 nanometers in length.

This diagram breaks down the electromagnetic spectrum by frequency and size of wavelengths. Notice the rainbow-colored section of visible light.
Diagram of the electromagnetic spectrum

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Video Transcript

Heinrich Hertz and Electromagnetic Waves

Who is Heinrich Hertz? If you guessed that he was the founder of the popular American car rental company with a similar name, you're not alone. But Heinrich Hertz wasn't a car rental entrepreneur. Instead, he was a German scientist who performed experiments with electricity when electricity was still a fancy new thing that scientists had a lot to learn about.

In 1888, when Hertz was 30, he made an electric spark jump from one terminal to another and noticed a second spark at the same time between two terminals a couple of yards away. Exciting stuff, I know, but this was 1888, and what Hertz noticed was a different kind of electromagnetic wave that eventually came to be known as Hertzian waves.

A few years later, in 1896, a young Italian scientist named Guglielmo Marconi built on Hertz's discovery and created the first radio transmitter, sending radio signals for a mile. (A mile!) Hertzian waves are now called radio waves and are used every day, from listening to the radio to watching TV.

What are Electromagnetic Waves?

We are surrounded by waves we can see and hear, from ocean waves to sound waves. A wave shows the transfer of energy, from the wind that starts an ocean wave to the sound that moves through the air to your ear drum. Waves that pass through a physical object or medium are called mechanical waves. Unlike mechanical waves, electromagnetic waves do not need a medium to travel or propagate. Electric and magnetic fields both produce vibrations and, together, the two types of energy create electromagnetic waves.

Waves take different shapes, but electromagnetic waves all have a snake-like shape which makes them transverse waves. Transverse waves are measured by their height, or amplitude, and by their wavelength, or the distance between the highest point of one wave, the crest, to the crest of the next wave. The lowest point of a wave is called a trough. Trough to trough can be measured, too. When analyzing an electromagnetic wave, both the amplitude and distance between waves is measured.

We measure both the amplitude, or height of a wave (a), and the distance between waves (b).
Diagram of a wavelength

One whole wave, from crest to crest, or trough to trough, is called a cycle. The number of cycles that occur per second is the wave's frequency. In honor of Heinrich Hertz, we measure frequency in hertz or Hz.

Types of Electromagnetic Waves

Electromagnetic waves are ordered on the electromagnetic spectrum by frequency. They range from radio waves with fewer cycles per second to the extraordinarily fast and harmful high frequency of gamma rays.

Radio waves have the lowest frequency of the seven bands of waves on the electromagnetic spectrum, which also means they have the least amount of energy. Radio waves have wavelengths measuring from miles to the length of a football, or around 11 inches.

It is common to talk about the frequency of radio waves, or the number of waves per second. When tuning in to a radio station, a person is listening to a specific frequency of radio waves. AM stations are numbered from 520 to 1610, with each number representing the frequency of the station at thousands of hertz per second, or kilohertz, abbreviated kHz. FM station frequencies range from 87.0 to 107.9 million hertz per second, called megahertz or MHz.

Sound is converted into EM waves and sent through radio dishes like this one. Your radio then receives these radio waves and changes them back into sound waves.
Image of a radio satellite

Next on the spectrum are microwaves, a type of radio wave that are less than 11.8 inches long. The microwaves people use to heat food have waves measuring about five inches. Microwaves aren't just for heating leftovers or cups of coffee, though. Microwaves are also used for radar, television and satellites.

Microwaves occur at higher frequencies, with billions or even trillions of cycles occurring per second. Since writing out 4,000,000 hertz is kind of clunky, it would be written as 4 gigahertz or 4 GHz. Digital radio is broadcast at a frequency of 2.5 billion hertz per second, or 2.5 GHz.

Infrared waves occur at an even higher frequency than microwaves. Infrared waves are used to power television remote controls and for thermal imaging, like when using a pair of night vision goggles. When you feel warmed by the sunlight, the energy you feel is infrared radiation from the sun. Since infrared waves have such high frequencies, their wavelengths are so tiny they are only hundredths or thousandths of an inch.

All electromagnetic waves are light, but the band of the electromagnetic spectrum that people and animals can see is called visible light. When a beam of light passes through a prism, a person can see each color of the rainbow separated into their individual wavelengths. Red, the longest of the wavelengths, measures around 700 nanometers; yellow is around 600 nanometers; and violet, the shortest, is around 400 nanometers in length.

This diagram breaks down the electromagnetic spectrum by frequency and size of wavelengths. Notice the rainbow-colored section of visible light.
Diagram of the electromagnetic spectrum

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Frequently Asked Questions

What are the seven electromagnetic waves?

The seven types of electromagnetic waves are radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. The preceding list is in order from lowest frequency and least energetic (radio waves) to highest frequency and most energetic (gamma rays).

Are electromagnetic waves mechanical waves?

Electromagnetic waves are not mechanical waves. They do not travel through a medium and they do not have mass. They do carry energy, however.

What is the meaning of electromagnetic waves?

Electromagnetic waves are simultaneous periodic oscillations in the intensity of an electromagnetic field. One probably knows them better as "light."

Are electromagnetic waves transverse?

Electromagnetic fields are indeed transverse waves. This means that they travel in a direction perpendicular to their direction of oscillation.

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