The 7 Major Regions of the Electromagnetic Spectrum

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  • 0:08 The Electromagnetic Spectrum
  • 0:36 Radio, Microwave, and…
  • 2:26 Visible Light and…
  • 3:46 Ultraviolet, X-Rays,…
  • 5:39 Lesson Summary
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Lesson Transcript
Instructor: April Koch

April teaches high school science and holds a master's degree in education.

This lesson will walk you through each of the major regions of the electromagnetic spectrum. Explore the unique characteristics of X-rays, microwaves, radio waves, UV rays, infrared, gamma rays, and of course, visible light.

The Electromagnetic Spectrum

Frequencies are defined on the electromagnetic spectrum.
Electromagnetic Spectrum Diagram

In previous lessons, we've learned about waves and their basic properties, including the very intriguing electromagnetic waves. EM waves originate from the vibration of charged particles, and they can travel without a medium. The electromagnetic spectrum describes the vast range of frequencies, from the lowest frequency radio waves to the highest frequency gamma rays. Now that we have a feel for how the EM spectrum works, we need to take a closer look at each separate region. Let's start with the radio waves and work our way up the spectrum.

Radio, Microwave, and Infrared

The lowest frequency waves on our EM spectrum are the radio waves. These are the waves that television and radio stations use to transmit data. By exciting the electrons on a conducting antenna, these stations create radio waves that can be received by other devices. The data is created by modulating the parameters of the oscillations; for instance, by changing the amplitude and the wavelength. Radio waves have the longest wavelengths, ranging from about one millimeter to hundreds of meters.

After radio waves come the microwaves. These, of course, are the waves used to heat your food in a microwave oven. They do this by rotating the molecules inside your food, which increases its thermal energy. Unlike regular ovens, microwave ovens do not actually transfer heat to your food. They heat the food directly by exciting the molecules. Microwaves are also used in wi-fi technology, but only at low intensities.

Infrared radiation is the next region on the electromagnetic spectrum. We call it infrared because it's just 'below' the red part of the visible spectrum. It spans from frequencies of about 300 gigahertz to about 400 terahertz. This is the same as a range of wavelengths from one millimeter to 750 nanometers. Infrared radiation is emitted by things that are warm or hot, including animals and people. We can see radiation in the infrared range only by using special technology.

Infrared radiation can only be seen with technical equipment.
Infrared Seen with Technology

We often use infrared photography to capture thermal images in the dark. Some animals can see in the infrared range, which allows them to accurately locate their prey. For example, a snake can use infrared vision to locate a warm mouse hiding in a grassy field. Mosquitoes can literally see the warm parts of your skin. This helps them pick out the best places to suck your blood!

Visible Light and Region Overlap

The region of visible light waves is pretty small compared to most other regions. This part of the spectrum is defined as the range of light frequencies to which the human eye is most sensitive. Visible light spans from about 760 to 380 nanometers. At the low-frequency end, we perceive the light as red. The full spectrum of visible colors spans through this range until we get to the other end, which we see as violet. We're going to talk more about colors in light in another lesson, so we won't worry about the exact parameters right now.

This is probably a good time to point out that the EM spectrum regions do overlap a little. For example, some of the low frequency infrared waves can also be considered microwaves, while some of the higher infrared waves overlap with the visible light range. Just like the colors green and blue blend into one another on the visible light spectrum, the ranges for each type of wave blend into one another on the electromagnetic spectrum.

The gases in the atmosphere of the earth absorb most harmful UV rays.
UV Waves Absorbed by Atmosphere

Scientists have generally classified waves based on how their radiation affects matter. For example, microwaves make molecules rotate, while infrared radiation makes molecules vibrate. In the overlap between microwaves and infrared, you might see properties of both. But let's not worry about the molecular effects of EM waves right now. We first need to make sure we know the rest of the EM spectrum.

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