Unit+3+Electromagnetic+Spectrum

**__Measuring the electromagnetic spectrum __**
=You actually know more about it than you may think! The [|electromagnetic (EM) spectrum] is just a name that scientists give a bunch of types of [|radiation] when they want to talk about= =them as a group. Radiation is energy that travels and spreads out as it goes-- [|visible light] that comes from a lamp in your house and [|radio waves] that come from a radio station are two types of electromagnetic radiation. Other examples of EM radiation are [|microwaves], [|infrared] and[|ultraviolet] light, [|X-rays] and [|gamma-rays]. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays.=

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=Here are the different types of radiation in the EM spectrum, in order from lowest energy to highest: = [|Microwaves] : They will cook your popcorn in just a few minutes! Microwaves in space are used by [|astronomers] to learn about the structure of nearby galaxies, and our own Milky Way || UV || [|Infrared] : Our skin emits infrared light, which is why we can be seen in the dark by someone using night vision goggles. In space, IR light maps the [|dust] between stars. [|Visible] <span style="color: #000099; font-family: Arial,sans-serif;">: Yes, this is the part that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars ... also by fast-moving particles hitting other particles. <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|Ultraviolet] <span style="color: #000099; font-family: Arial,sans-serif;">: We know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn! Stars and other "hot" objects in space emit UV radiation. || <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|X-rays] : Your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the<span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|Universe] also emit X-rays. || <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|Gamma-rays] : Radioactive materials (some natural and others made by man in things like nuclear power plants) can emit gamma-rays. Big particle accelerators that scientists use to help them understand what <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|matter] is made of can sometimes generate gamma-rays. But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways. || =[[http://Many%20different%20kinds%20of%20energy%20travel%20in%20waves.%20Sound%20waves%20carry%20noises%20through%20the%20air%20to%20our%20ears.%20SEISMIC%20WAVES%20travel%20inside%20the%20Earth%20and%20cause%20earthquakes.%20Light,%20heat,%20radio,%20and%20similar%20types%20of%20energy%20are%20carried%20by%20a%20variety%20of%20waves%20in%20the%20ELECTROMAGNETIC%20SPECTRUM.%20Some%20energy%20waves%20need%20a%20medium,%20such%20as%20water%20or%20air,%20through%20which%20to%20travel.%20The%20medium%20moves%20back%20and%20forth%20as%20waves%20carry%20energy%20through%20it,%20but%20it%20does%20not%20actually%20travel%20along%20with%20the%20wave.%20%20%20Suppose%20you%20fix%20a%20slinky%20spring%20at%20one%20end%20and%20push%20the%20other%20end%20back%20and%20forth.%20Some%20parts%20of%20the%20spring,%20called%20compressions,%20are%20squeezed%20together.%20Other%20parts%20of%20the%20spring,%20called%20rarefactions,%20are%20stretched%20out.%20The%20compressions%20and%20rarefactions%20travel%20down%20the%20spring%20carrying%20energy.%20This%20type%20of%20wave%20is%20called%20a%20longitudinal%20or%20compression%20wave.%20%20%20Suppose%20you%20fix%20the%20slinky%20at%20one%20end%20and%20move%20it%20up%20and%20down.%20Energy%20travels%20along%20the%20spring%E2%80%99s%20length%20in%20S-shaped%20waves,%20so%20the%20forward%20direction%20in%20which%20the%20energy%20moves%20is%20at%20right%20angles%20(or%20transverse)%20to%20the%20up-and-down%20direction%20of%20the%20movement%20of%20the%20spring.%20This%20is%20called%20a%20transverse%20wave.%20%20%20Waves%20have%20three%20important%20measurements.%20The%20amplitude%20is%20the%20height%20of%20a%20peak%20or%20trough.%20The%20wavelength%20is%20the%20distance%20between%20any%20two%20peaks%20or%20troughs.%20The%20frequency%20is%20the%20number%20of%20waves%20that%20pass%20by%20in%20one%20second.%20Amplitude%20and%20wavelength%20are%20measured%20in%20metres.%20Frequency%20is%20measured%20in%20hertz%20(Hz).%20One%20Hz%20is%20equal%20to%20one%20wave%20passing%20by%20each%20second.%20%20%20%20Read%20more:%20ENERGY%20WAVES%20%E2%80%94%20Infoplease.com%20http://www.infoplease.com/dk/science/encyclopedia/energy-waves.html#ixzz1aJBlzwll|Understanding Energy Waves Website]]=
 * || <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|Radio] : Yes, this is the same kind of energy that radio stations emit into the air for your boom box to capture and turn into your favorite Mozart, Madonna, or Justin Timberlake tunes. But radio waves are also emitted by other things ... such as <span style="background-color: #e3effa; color: #ff0000; font-family: arial,helvetica,verdana,sans-serif; text-decoration: none;">[|stars] and gases in space. You may not be able to dance to what these objects emit, but you can use it to learn what they are made of. ||
 * Microwave || [[image:http://imagine.gsfc.nasa.gov/Images/introduction/spectrum_microwave.gif caption="Microwave"]]
 * Infrared to
 * Infrared to
 * x-ray || [[image:http://imagine.gsfc.nasa.gov/Images/introduction/spectrum_xray.gif caption="X-ray"]]
 * x-ray || [[image:http://imagine.gsfc.nasa.gov/Images/introduction/spectrum_xray.gif caption="X-ray"]]
 * Gamma-ray || [[image:http://imagine.gsfc.nasa.gov/Images/introduction/spectrum_gamma.gif caption="Gamma-ray"]]
 * Gamma-ray || [[image:http://imagine.gsfc.nasa.gov/Images/introduction/spectrum_gamma.gif caption="Gamma-ray"]]

<span style="color: #0000ff; font-family: Lucida,;">**ELECTROMAGNETIC SPECTRUM**
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">Radios, televisions, mobile phones, and radar use signals made up of electromagnetic waves. These are waves that carry energy as electricity and magnetism at the speed of light. Light we can see is also an electromagnetic wave, but other types of electromagnetic waves are invisible. The various types of electromagnetic waves have different frequencies and wavelengths. Together, they make up the electromagnetic spectrum.
 * [[image:http://www.infoplease.com/images/ESCI099ELESPE002.jpg align="left" caption="X-RAYS"]] ||
 * X-RAYS ||

<span style="color: #0033cc; font-family: Lucida,;">X-RAYS
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">**These are high-energy waves that pass through flesh but not bone. In medicine, X-ray photographs are used to check people's bones for damage. In high doses, X-rays can harm people.**

Gamma Rays

 * These are produced by radioactivity. They have a short wavelength and a high frequency and carry large amounts of energy. They are**
 * very harmful and can cause cancer in humans and animals.**

<span style="color: #0033cc; font-family: Lucida,;">ULTRAVIOLET RAYS
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">**These invisible waves are slightly shorter than visible violet light and carry more energy. We wear sunglasses and sunblock to prevent damage to our eyes and skin by ultraviolet rays.**



<span style="color: #0033cc; font-family: Lucida,;">INFRARED RAYS
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">**Infrared rays are slightly longer waves than visible red light. Although we cannot see infrared, we can feel it as heat. When heat energy is transferred by radiation, it is carried by waves of infrared.**

<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">

<span style="color: #0033cc; font-family: Lucida,;">RADAR
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">**Radar is a way of locating aeroplanes and ships using a type of radio waves called microwaves. These have much longer wavelengths than visible light. Cooking is another use for microwaves**.

<span style="color: #0033cc; font-family: Lucida,;">RADIO WAVES
<span style="color: #000000; font-family: Helvetica,Arial,Lucida,;">**Radio waves are the longest in the spectrum. They carry radio and TV signals around Earth. Radio waves from outer space are picked up by radio telescopes and used in studies of the universe**.

=Tutorials and Videos= [|Electromagnetic Spectrum Overview] [|Electromagnetic Spectrum Tutorial] [|Test Your Knowledge of the Electromagnetic Spectrum] [|Matching Game]

=Extension/Enrichment:=
 * [|Extension on wavelenghts and the spectrum]**



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