Electromagnetic RadiationThere are waves of energy and light moving all around us in the form of TV and audio transmissions, gamma radiation from space, and heat in the atmosphere. Scientists call them all electromagnetic radiation. The waves of energy are called electromagnetic (EM) because they have both electric and magnetic characteristics. Scientists classify them by the frequency of their wavelength, going from high to low frequency. When a wave has a lot of energy, it could be a gamma ray or x-ray. If it has low frequency, it has less energy and could be a TV or radio wave.
Particles And WavesAll EM energy waves travel at the speed of light. No matter what their frequency or wavelength, they always move at the same speed. Some properties of waves, such as diffraction and interference, are also seen in EM radiation. Scientists have figured out that there are tiny particles in these waves. Those particles are called photons. The photons are specific units, or packets, of energy. Sometimes those particles interact with each other and change the way the light originally behaved.
All types of EM radiation are useful to the world of science. Look at radio waves as an example. Radio stations and ham radio operators of Earth work with radio waves every day. Radio waves are used to carry communications from one point to another. Radio waves are also extremely important to astronomers. Astronomers are constantly listening to the radio waves of other galaxies to learn more about their stars. Stars give off large amounts of EM radiation across the entire spectrum, and we can study that radiation to learn more about the universe.
Bookends Of Visible LightBeyond the usual visible light, you will hear geographers talk about infrared and ultra-violet radiation. Infrared should be easy for you to remember because it is heat. Every object in the Universe has a temperature. Even space has some energy. The Earth has infrared radiation, you have a little more (because you are warmer), and a star gives off a huge amount (it's super-hot). Ultra violet is just a bit more powerful than visible light in the violet range. Objects on Earth don't give off much ultra-violet radiation, but the Sun gives off huge amounts. The Sun is a big source of UV radiation because of all of its nuclear reactions.
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Tour the EM Spectrum (ScienceAt NASA Video)
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