What is the Electromagnetic Spectrum?
By: Cameron F.
2012
Introduction
In 1873, James Clerk Maxwell published a theory on the electromagnetic spectrum. He believed that radiation moved at the speed of light across space. Scientist use the name electromagnetic spectrum to refer to the different types of radiation as a group. Some radiation you can see, others you can feel or hear, and yet others you cannot sense at all. Each type of radiation has its own uses. For instance, some radiation is used for communication like radios, telephones and television.

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Figure 1 James Clerk Maxwell

Types of Electromagnetic Radiation
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Figure 2 Examples of the Electromagnetic Spectrum

Radio waves are used for wireless transmission of sound, information, communication, and aircraft navigation.
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Microwaves cook your dinner in minutes and help scientist learn about the universe.
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Infrared light is beyond the end of the visible range for humans. Night vision goggles helps our military see the infrared light given off by our skin.
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Visible light is the only part of the spectrum that the human eye can see.
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Ultraviolet light is produced by the sun and can cause sun burn. UVB is the main source of sun burn and skin cancer.
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X-rays are used by doctors to see our bones for medical treatment.
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Gamma waves are emitted by nuclear power plants and by our universe. Gamma rays are to treat cancer.
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Radiation
Radiation is made up of photons that travel at the speed of light. Photons are massless particles that contain energy. These photons travel in a wavelike pattern. Scientist measure the wavelength from crest to crest or top to top of the wave.


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Figure 3 How to Measure a Wavelength


How to measure Frequency

Scientist also measure the energy contained by the radiation wave form by measuring the frequency. Frequency is measured in Hertz or cycles per second. You measure frequency by counting how many times per second a wave moves across the line of zero. Radio waves have the lowest frequency but the longest wavelength and Gamma waves have the highest frequency but the shortest wave length.





Electromagnetic spectrum and wavelength

The electromagnetic spectrum can be ordered from longest wavelength and lowest energy to shortest wavelength and highest energy starting from radio waves, microwave, infrared, visible, ultraviolet, X-Rays, and ending with Gamma rays.

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Figure 5 Electromagnetic Spectrum and Wavelength


Interesting Facts
  • You deal with the electromagnetic spectrum every day. You use radio waves every day when you when you watch your favorite TV show, listen to the newest hit song on the radio or talk to your friends on the phone.
  • You tune into a station by stetting your radio to the same frequency as the radio station is sending out its waves.
  • The universe is the biggest producer of gamma-rays.
  • The wavelength of a radio wave can be the large as the length of a football field.
  • The wavelength of visible light can be as small as a virus.
  • Each color of the rainbow has its own wavelength. Red has the longest wavelength, then orange, yellow, green, blue, indigo and violet.


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Figure 6 Wavelengths of the Colors of the Rainbow

Glossary of Terms
Crest – top of wave
Electromagnetic wave – electric and magnetic charges that apply influence
Frequency- How many times a wave crosses the line of zero; the unit of measure is Hertz (cycles) per second.
Photons- massless particles that contain energy
Radiation - photons that travel in waves at the speed of light
Spectrum – a continuous group or range of objects such as waves
Though – valley or bottom of wave
Wavelength – length of the wave measured from crest to crest




Citations

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Mattson, Barb. “The Electromagnetic Spectrum.” NASA Goddard Space Flight Center. NASA, 3/2/2010. Web. 26 September 2012.



McGrath, Kimberley A., ed. The Gale Encyclopedia of Science. Vol. 2. Detroit: Gale Group, 2001. Print.

Netting, Ruth. “The Electromagnetic Spectrum.” National Aeronautics and Space Administration. NASA. 25 February 2011. Web. 21 September, 2012.

"Physics." Compton's by Britannica. Encyclopedia Britannica Online School Edition.



Encyclopedia Britannica, Inc., 2012. Web. 26 Sept. 2012.



Science Mission Directorate. "Introduction to the Electromagnetic Spectrum" Mission: Science. 2010. National Aeronautics and Space Administration. 26 Sep. 2012

Silverstein, Alvin, Virginia Sliverstein, and Laura Silverstein Nunn. Energy. Brookfield: Twenty-First Century Books, 1998. Print.



Physics: A World in Motion: Biomedical Applications of EMR. Prod. Distribution Access. Alberta Education, 1998. Discovery Education. Web. 21 September 2012.