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electromagnetic spectrum | Definition, Diagram, & Uses

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Electromagnetic spectrum: Electromagnetic spectrum, the entire distribution of electromagnetic radiation according to frequency or wavelength.

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Kids.Net.Au - Encyclopedia > Electromagnetic spectrum

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Kids.Net.Au - Encyclopedia > Electromagnetic spectrum

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The Science of Light and Color for Kids: Rainbows and the Electromagnetic Spectrum - FreeSchool

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Physics for Kids: Types of Electromagnetic Waves

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Kids learn about the types of electromagnetic waves in the science of physics including microwaves, infrared, ultraviolet, radio, x-rays, and gamma rays.

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This interactive looks at the electromagnetic spectrum.

The electromagnetic spectrum is a classification of the Sun's radiation. Scientists have identified solar energy as a spectrum of many different wavelengths of electromagnetic rays. They have called this the electromagnetic spectrum. Click on each wavelength to learn more about the waves that make up the spectrum.

Transcript

Radio

Radio waves have the longest wavelengths in the electromagnetic spectrum. They are used to transport information through the atmosphere without wires. They carry signals to your radio, television and mobile phone.

Astronomers like Melanie Johnston-Hollitt use radio telescopes that receive radio waves emitted by planets, stars, galaxies, and nebulas to study the far reaches of the universe.

Image acknowledgement: Galaxies show as small radio emissions in this telescopic image by Melanie Johnston-Hollitt

Microwave

Microwaves have wavelengths that can be measured in centimetres. Microwaves are widely used in modern technology. They are used for diverse applications like heating food in a microwave oven, garage door openers, particle accelerators and for transmitting information from one place to another. Shorter microwaves can be used for radar, like the Doppler radar used in weather forecasts.

Image acknowledgement: Andriy Popov, 123RF Ltd

Infrared

Infrared light has a range of wavelengths. 'Near infrared' has shorter wavelengths and is used for devices such as night vision goggles. 'Far infrared' has longer wavelengths and is used for things such as thermal imaging. In the thermal image above the left hand cup holds a hot drink and the right hand cup a cold drink. The coolest parts are dark blue and the hottest parts have been coloured white to signal a temperature of 55° Celsuis and beyond.

Infrared can also be used for some short range 'line of sight' communication, such as TV remote controls.

Image acknowledgement: University of Waikato

Visible light

Visible light waves are the only electromagnetic waves we can see. We see these waves as the colours of the rainbow. Each colour has a different wavelength. Red has the longest wavelength, and violet has the shortest wavelength. When all the waves are seen together, they make white light.

Image acknowledgement : Delcreations, 123RF Ltd

Ultraviolet

There are several regions to ultraviolet light in the electromagnetic spectrum, ranging in wavelength between 10 and 400 nanometres. Too much exposure to UV light (such as that emitted from our Sun) can cause harmful effects like sunburn. However, ultraviolet light has been used for things such as UV lasers, fluorescent lamps and disinfecting wastewater.

Image acknowledgement: University of Waikato

X-ray

X-rays have one of the smallest wavelengths in the electromagnetic spectrum. They have higher energy than ultraviolet light, but longer wavelengths than gamma rays. X-rays are primary used for diagnostic radiography. They are formed through ionizing radiation, and too much exposure (the radiation is too intense and/or you are exposed for too long) can be dangerous.

Image acknowledgement : University of Waikato

Gamma

Gamma rays have the smallest wavelengths in the electromagnetic spectrum. They have the most energy of any wave. The waves are generated by radioactive processes such as in nuclear explosions. Like other areas of the electromagnetic spectrum, they can be used to kill living cells, such as cancer, but can provoke DNA alteration by interfering with the genetic material of the cell.

Image acknowledgement: A nuclear test conducted by the United States in 1953 in the Nevada Desert. Public domain.

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This interactive looks at the electromagnetic spectrum.

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NOVA | The Electromagnetic Spectrum | Season 39 | Episode 7

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NOVA Labs: Most of what we know about solar science comes from reading the Sun's light.

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What is Light? Maxwell and the Electromagnetic Spectrum

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The Sun is constantly broadcasting information about its activity in the form of light waves. Find out why there's more to see than what meets the eye...

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Introduction to electromagnetic waves

Electromagnetic radiation is one of the many ways that energy travels through space. The heat from a burning fire, the light from the sun, the X-rays used by your doctor, as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation. While these forms of energy might seem quite different from one another, they are related in that they all exhibit wavelike properties.

While it's good to have a basic understanding of what electromagnetic radiation is, most chemists are less interested in the physics behind this type of energy, and are far more interested in how these waves interact with matter. More specifically, chemists study how different forms of electromagnetic radiation interact with atoms and molecules. From these interactions, a chemist can get information about a molecule's structure, as well as the types of chemical bonds it contains. Before we talk about that, however, it's necessary to talk a little bit more about the physical properties of light waves.

Basic properties of waves: Amplitude, wavelength, and frequency

As you might already know, a wave has a trough (lowest point) and a crest (highest point). The vertical distance between the tip of a crest and the wave's central axis is known as its amplitude. This is the property associated with the brightness, or intensity, of the wave. The horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave. These lengths can be visualized as follows:

Keep in mind that some waves (including electromagnetic waves) also oscillate in space, and therefore they are oscillating at a given position as time passes. The quantity known as the wave's frequency refers to the number of full wavelengths that pass by a given point in space every second; the SI unit for frequency is Hertz , which is equivalent to "per seconds" written as or . As you might imagine, wavelength and frequency are inversely proportional: that is, the shorter the wavelength, the higher the frequency, and vice versa. This relationship is given by the following equation:

To illustrate the relationship between frequency and wavelength, let's consider an example.

Example: Calculating the wavelength of a light wave

We can start with our equation that relates frequency, wavelength, and the speed of light.

Next, we rearrange the equation to solve for wavelength.

Lastly, we plug in our given values and solve.

Now that we have an understanding of some basic properties of waves, we'll look at the different types of electromagnetic radiation.

The electromagnetic spectrum

Electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies; this classification is known as the electromagnetic spectrum. The following table shows us this spectrum, which consists of all the types of electromagnetic radiation that exist in our universe.

As we can see, the visible spectrum-that is, light that we can see with our eyes-makes up only a small fraction of the different types of radiation that exist. To the right of the visible spectrum, we find the types of energy that are lower in frequency (and thus longer in wavelength) than visible light. These types of energy include infrared (IR) rays (heat waves given off by thermal bodies), microwaves, and radio waves. These types of radiation surround us constantly, and are not harmful, because their frequencies are so low. As we will see in the section, "the photon," lower frequency waves are lower in energy, and thus are not dangerous to our health.

To the left of the visible spectrum, we have ultraviolet (UV) rays, X-rays, and gamma rays. These types of radiation are harmful to living organisms, due to their extremely high frequencies (and thus, high energies). It is for this reason that we wear suntan lotion at the beach (to block the UV rays from the sun) and why an X-ray technician will place a lead shield over us, in order to prevent the X-rays from penetrating anything other than the area of our body being imaged. Gamma rays, being the highest in frequency and energy, are the most damaging. Luckily though, our atmosphere absorbs gamma rays from outer space, thereby protecting us from harm.

Next, we will talk about the relationship between a wave's frequency and its energy.

Quantization of energy and the dual nature of light

Planck's discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave. In actuality, light seemed to have both wavelike and particle-like properties.

Planck's discoveries paved the way for the discovery of the photon. A photon is the elementary particle, or quantum, of light. As we will soon see, photons can be absorbed or emitted by atoms and molecules. When a photon is absorbed, its energy is transferred to that atom or molecule. Because energy is quantized, the photon's entire energy is transferred (remember that we cannot transfer fractions of quanta, which are the smallest possible individual "energy packets"). The reverse of this process is also true. When an atom or molecule loses energy, it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule. This change in energy is directly proportional to the frequency of photon emitted or absorbed. This relationship is given by Planck's famous equation:

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Light: Electromagnetic waves, the electromagnetic spectrum and photons (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Like science? Please donate to help EarthSky keep going. Rather donate via PayPal or send a check? Click here.
When you think of light, you probably think of what your eyes can see. But the light to which our eyes are sensitive is just the beginning; it is a sliver of the total amount of light that surrounds us. The electromagnetic spectrum is the term used by scientists to describe the entire range of light that exists. From radio waves to gamma rays, most of the light in the universe is, in fact, invisible to us!

Light is a wave of alternating electric and magnetic fields. The propagation of light isn't much different than waves crossing an ocean. Like any other wave, light has a few fundamental properties that describe it. One is its frequency, measured in Hertz, which counts the number of waves that pass by a point in one second. Another closely related property is wavelength: the distance from the peak of one wave to the peak of the next. These two attributes are inversely related. The larger the frequency, the smaller the wavelength - and vice versa.

The electromagnetic waves your eyes detect - visible light - oscillates between 400 and 790 terahertz (THz). That's several hundred trillion times a second. The wavelengths are roughly the size of a large virus: 390 - 750 nanometers (1 nanometer = 1 billionth of a meter). Our brain interprets the various wavelengths of light as different colors. Red has the longest wavelength, and violet the shortest. When we pass sunlight through a prism, we see that it's actually composed of many wavelengths of light. The prism creates a rainbow by redirecting each wavelength out a slightly different angle.

But light doesn't stop at red or violet. Just like there are sounds we can't hear (but other animals can), there is also an enormous range of light that our eyes can't detect. In general, the longer wavelengths come from the coolest and darkest regions of space. Meanwhile, the shorter wavelengths measure extremely energetic phenomena.

Astronomers use the entire electromagnetic spectrum to observe a variety of things. Radio waves and microwaves - the longest wavelengths and lowest energies of light - are used to peer inside dense interstellar clouds and track the motion of cold, dark gas. Radio telescopes have been used to map the structure of our galaxy while microwave telescopes are sensitive to the remnant glow of the Big Bang.

Infrared telescopes excel at finding cool, dim stars, slicing through interstellar dust bands, and even measuring the temperatures of planets in other solar systems. The wavelengths of infrared light are long enough to navigate through clouds that would otherwise block our view. By using large infrared telescopes, astronomers have been able to peer through the dust lanes of the Milky Way into the core of our galaxy.

The majority of stars emit most of their electromagnetic energy as visible light, the tiny portion of the spectrum to which our eyes are sensitive. Because wavelength correlates with energy, the color of a star tells us how hot it is: red stars are coolest, blue are hottest. The coldest of stars emit hardly any visible light at all; they can only be seen with infrared telescopes.

At wavelengths shorter than violet, we find the ultraviolet, or UV, light. You may be familiar with UV from its ability to give you a sunburn. Astronomers use it to hunt out the most energetic of stars and identify regions of star birth. When viewing distant galaxies with UV telescopes, most of the stars and gas disappear, and all the stellar nurseries flare into view.

Beyond UV, comes the highest energies in the electromagnetic spectrum: X-rays and gamma rays. Our atmosphere blocks this light, so astronomers must rely on telescopes in space to see the x-ray and gamma ray universe. X-rays come from exotic neutron stars, the vortex of superheated material spiraling around a black hole, or diffuse clouds of gas in galactic clusters that are heated to many millions of degrees. Meanwhile, gamma rays - the shortest wavelength of light and deadly to humans - unveil violent supernova explosions, cosmic radioactive decay, and even the destruction of antimatter. Gamma ray bursts - the brief flickering of gamma ray light from distant galaxies when a star explodes and creates a black hole - are among the most energetic singular events in the universe.

Bottom line: the electromagnetic spectrum describes all the wavelengths of light - both seen and unseen. The shorter the wavelength, the more energetic the light. By using telescopes sensitive to different wavelength ranges of the spectrum, astronomers get a glimpse into a wide variety of objects and phenomena in the universe.

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What is the electromagnetic spectrum? | EarthSky.org

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Like science? Please donate to help EarthSky keep going. Rather donate via PayPal or send a check? Click here. When you think of light, you probably think of what your eyes can see. But the light to which our eyes are sensitive is just the beginning; it is a sliver of the total amount of light that surrounds us.

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The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves, infrared light, ultraviolet light, X-rays and gamma-rays.

You know more about the electromagnetic spectrum than you may think. The image below shows where you might encounter each portion of the EM spectrum in your day-to-day life.

Is a radio wave the same as a gamma ray?

Are radio waves completely different physical objects than gamma-rays? They are produced in different processes and are detected in different ways, but they are not fundamentally different. Radio waves, gamma-rays, visible light, and all the other parts of the electromagnetic spectrum are electromagnetic radiation.

Electromagnetic radiation can be described in terms of a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light. Each photon contains a certain amount of energy. The different types of radiation are defined by the the amount of energy found in the photons. Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.

Measuring electromagnetic radiation

Electromagnetic radiation can be expressed in terms of energy, wavelength, or frequency. Frequency is measured in cycles per second, or Hertz. Wavelength is measured in meters. Energy is measured in electron volts. Each of these three quantities for describing EM radiation are related to each other in a precise mathematical way. But why have three ways of describing things, each with a different set of physical units?

The short answer is that scientists don't like to use numbers any bigger or smaller than they have to. It is much easier to say or write "two kilometers" than "two thousand meters." Generally, scientists use whatever units are easiest for the type of EM radiation they work with.

Astronomers who study radio waves tend to use wavelengths or frequencies. Most of the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30 gigahertz (GHz) to 300 kilohertz (kHz) in frequencies. The radio is a very broad part of the EM spectrum.

Infrared and optical astronomers generally use wavelength. Infrared astronomers use microns (millionths of a meter) for wavelengths, so their part of the EM spectrum falls in the range of 1 to 100 microns. Optical astronomers use both angstroms (0.00000001 cm, or ) and nanometers (0.0000001 cm, or ). Using nanometers, violet, blue, green, yellow, orange, and red light have wavelengths between 400 and 700 nanometers. (This range is just a tiny part of the entire EM spectrum, so the light our eyes can see is just a little fraction of all the EM radiation around us.)

The wavelengths of ultraviolet, X-ray, and gamma-ray regions of the EM spectrum are very small. Instead of using wavelengths, astronomers that study these portions of the EM spectrum usually refer to these photons by their energies, measured in electron volts (eV). Ultraviolet radiation falls in the range from a few electron volts to about 100 eV. X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-rays then are all the photons with energies greater than 100 keV.

Show me a chart of the wavelength, frequency, and energy regimes of the spectrum

Why do we put telescopes in orbit?

Most electromagnetic radiation from space is unable to reach the surface of the Earth. Radio frequencies, visible light and some ultraviolet light makes it to sea level. Astronomers can observe some infrared wavelengths by putting telescopes on mountain tops. Balloon experiments can reach 35 km above the surface and can operate for months. Rocket flights can take instruments all the way above the Earth's atmosphere, but only for a few minutes before they fall back to Earth.

For long-term observations, however, it is best to have your detector on an orbiting satellite and get above it all!

Updated: March 2013

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The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes - the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation.