Electromagnetic Spectrum
Jean Brainard, Ph.D.
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Printed: August 25, 2016
AUTHOR
Jean Brainard, Ph.D.
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C HAPTER
Chapter 1. Electromagnetic Spectrum
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Electromagnetic Spectrum
• Describe electromagnetic radiation and its properties.
• Give an overview of the electromagnetic spectrum.
It’s a warm sunny Saturday, and Michael and Lavar have a big day planned. They’re going to ride across town to
meet their friends and then go to the zoo. The boys may not realize it, but they will be bombarded by electromagnetic
radiation as they ride their bikes and walk around the zoo grounds. The only kinds of radiation they can detect are
visible light, which allows them to see, and infrared light, which they feel as warmth on their skin.
Q: Besides visible light and infrared light, what other kinds of electromagnetic radiation will the boys be exposed to
in sunlight?
A: Sunlight consists of all the different kinds of electromagnetic radiation, from harmless radio waves to deadly
gamma rays. Fortunately, Earth’s atmosphere prevents most of the harmful radiation from reaching Earth’s surface.
You can read about the different kinds of electromagnetic radiation in this article.
Electromagnetic Radiation
Electromagnetic radiation is energy that travels in waves across space as well as through matter. Most of the
electromagnetic radiation on Earth comes from the sun. Like other waves, electromagnetic waves are characterized
by certain wavelengths and wave frequencies. Wavelength is the distance between two corresponding points on
adjacent waves. Wave frequency is the number of waves that pass a fixed point in a given amount of time.
Electromagnetic waves with shorter wavelengths have higher frequencies and more energy.
A Spectrum of Electromagnetic Waves
Visible light and infrared light are just a small part of the full range of electromagnetic radiation, which is called the
electromagnetic spectrum. You can see the waves of the electromagnetic spectrum in the Figure 1.1. At the top of
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the diagram, the wavelengths of the waves are given. Also included are objects that are about the same size as the
corresponding wavelengths. The frequencies and energy levels of the waves are shown at the bottom of the diagram.
Some sources of the waves are also given.
FIGURE 1.1
• On the left side of the electromagnetic spectrum diagram are radio waves and microwaves. Radio waves have
the longest wavelengths and lowest frequencies of all electromagnetic waves. They also have the least amount
of energy.
• On the right side of the diagram are X rays and gamma rays. They have the shortest wavelengths and highest
frequencies of all electromagnetic waves. They also have the most energy.
• Between these two extremes are waves that are commonly called light. Light includes infrared light, visible
light, and ultraviolet light. The wavelengths, frequencies, and energy levels of light fall in between those of
radio waves on the left and X rays and gamma rays on the right.
Q: Which type of light has the longest wavelengths?
A: Infrared light has the longest wavelengths.
Q: What sources of infrared light are shown in the diagram?
A: The sources in the diagram are people and light bulbs, but all living things and most other objects give off infrared
light.
Summary
• Electromagnetic radiation travels in waves through space or matter. Electromagnetic waves with shorter
wavelengths have higher frequencies and more energy.
• The full range of electromagnetic radiation is called the electromagnetic spectrum. From longest to shortest
wavelengths, it includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X rays, and
gamma rays.
Review
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6.
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Describe the relationship between the wavelength and frequency of electromagnetic waves.
What is the electromagnetic spectrum?
Which electromagnetic waves have the longest wavelengths?
Identify a source of microwaves.
Which type of light has the highest frequencies?
Explain why gamma rays are the most dangerous of all electromagnetic waves.
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Chapter 1. Electromagnetic Spectrum
Resources
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/176491
References
1. Courtesy of NASA. The electromagnetic spectrum spans a wide range of wavelengths and frequencies . public
domain
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