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Electromagnetic Spectrum
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Defining Electromagnetic Spectrum
The electromagnetic spectrum is the collective noun describing
all of the types of radiation arranged by the amounts of energy
they carry.
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Radiation
!  Radiation is any movement of energy through space.
!  Think of the movement of radiation like a wave. This wave is
made up of many moving electrical and magnetic fields.
!  You can also think of radiation as a stream of particles called
photons.
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Electromagnetic (EM)Radiation
!  Sometimes acts like a wave/sometimes acts like a particle.
!  Seven types of EM Radiation
!  Radio waves (lowest energy level and increasing)
!  Microwaves
!  Infrared light
!  Visible light
!  Ultraviolet light
!  X-rays
!  Gamma rays
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Radio Waves
!  Radio waves are used to transmit radio and television signals.
!  AM radio uses low-energy waves
!  FM radio uses medium-energy waves
!  TV uses high-energy waves
!  Cell phones use radio waves
!  Stars in space can also emit radio waves
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Microwaves
!  Microwaves are used in microwaves ovens
!  Airplane radar systems use microwaves
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Infrared Rays
!  Often produced when an object radiates heat.
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  M radio uses medium-energy waves
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 TV uses high-energy waves
 Cell phones use radio waves
 Stars in space can also emit radio waves
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Microwaves
!  Microwaves are used in microwaves ovens
!  Airplane radar systems use microwaves
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Infrared Rays
!  Often produced when an object radiates heat.
!  You can’t see them, but you can feel them.
!  A remote control uses infrared rays to send signals to your TV
set, sound equipment, or games and even some toys.
!  Used to take photographs called thermographs.
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Visible Light
!  Humans can see visible light because of special cells called
cones.
!  Eyes can perceive wavelengths of visible light as color.
!  Colors are ordered from lowest to highest energy – ROYGBIV
Red>Orange>Yellow>Green>Blue>Indigo>Violet
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Ultraviolet Rays (UV)
!  Occur naturally in sunlight
!  The ozone blocks most UV radiation from reaching the surface
of the earth.
!  UV rays can cause skin cancer and cataracts when exposed
to large doses.
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X-Rays
!  X-rays have very high penetrating power.
!  A benefit of X-rays is the ability to take a picture of bones,
organs, and other difficult to see things – helping diagnose
and detect potential problems.
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Gamma Rays
!  The most energetic waves in the EM spectrum.
!  Most are absorbed by our atmosphere.
!  Some gamma rays are produced on Earth in certain highenergy reactions, such as nuclear explosions.
!  Gamma rays do a lot of damage when they pass through
living cells.
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Where Does Radiation Come From?
!  All matter is made up of atoms.
!  Each atom is made up of
!  Protons, neutrons, and electrons.
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Gamma Rays
!  The most energetic waves in the EM spectrum.
!  Most are absorbed by our atmosphere.
!  Some gamma rays are produced on Earth in certain highenergy reactions, such as nuclear explosions.
!  Gamma rays do a lot of damage when they pass through
living cells.
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Where Does Radiation Come From?
!  All matter is made up of atoms.
!  Each atom is made up of
!  Protons, neutrons, and electrons.
!  Electrons orbit around the proton and neutron nucleus at
different levels, or shells, depending on how much energy they
have.
!  When an electron drops from one energy level to another, it
gives off energy in the form of electromagnetic radiation.
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Final Facts
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  he sun, earth, and stars all radiate electromagnetic energy of
varying strengths.
!  All electromagnetic radiation moves through the universe at a
constant speed of 300,000 kilometers per second.
!  EM radiation can even travel through the empty vacuum of
outer space.
!  The higher the energy of the wave, the more it has the
opportunity to pass through matter.
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