Electromagnetic Waves

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Electromagnetic Waves

• Electromagnetic waves are transverse waves
  consisting of changing electrical fields and
  changing magnetic fields.
• Magnetic and electric fields of an
  electromagnetic wave are perpendicular to each
  other and to the direction of the wave.

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What are they?

• An electrical field is a region of space that
  exerts an electrical forces on charged particles.
• A magnetic field is a region of space that
  produce magnetic forces.
• Electromagnetic waves are produced when an
  electric charge vibrates or accelerates.
• Electromagnetic waves can travel through a vacuum
  or empty space, as well as through matter.

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Properties

• The speed of light in a vacuum (c)
• 3.00 x 108 meters per second
• In a vacuum all electromagnetic waves travel at
  the same speed, but their wavelength and
  frequency vary.
• The wavelength is inversely proportional to the
  frequency.
• s f? (speed c)

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Wave or Particle?

• Electromagnetic radiation behaves sometimes like
  a wave and sometimes like a stream of particles.
• Wave
• Light demonstrates it experiences interference.
• Particle
• Photoelectric Effect a metal plate can emit
  electrons if a high energy light
  (Blue-Ultraviolet) strikes it.
• The intensity of light decreases as photons
  travel farther from the source.

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The Waves of the Spectrum

• The full range of frequencies of electromagnetic
  radiation is called the Electromagnetic Spectrum.

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Large ? Low f

• Radio Waves are used in radio and television
  technologies, as well as in microwave ovens and
  radar.
• AM and FM radio waves has the lowest frequencies.
  
• Amplitude modulation (AM), the amplitude of the
  wave is varied, but the frequency stays the same.
  
• Frequency modulation (FM), the frequency of the
  wave is varied, but the amplitude stays the same.
• AM can be heard for a greater distance

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Detection

• The shortest wavelength radio waves are called
  microwaves.
• f300 MHz-300,000MHz
• Cook Food
• Cell Phone Communication
• Water and fat molecules absorb microwaves and
  their thermal energy increases.

• Radar (Radio Detection And Ranging)
• Radio waves are sent out in short bursts and the
  waves reflect off the objects and bounce back to
  the receiver.
• Doppler is used to determine speeds of moving
  objects.

Right Now on Doppler
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Infrared Rays

• Infrared rays have a wavelength of 1 mm 1nm
• Infrared rays are used as a source of heat and to
  discover areas of heat differences.
• Thermograms are color-coded pictures that show
  variation in temperature.

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Visible Light

• Visible light is light is the part of the EM
  spectrum the human eye can see.
• Each color corresponds to a specific frequency
  and wavelength.

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Ultraviolet Rays

• Ultraviolet rays have applications in health and
  medicine, and in agriculture.
• The wavelengths vary from 400nm-4nm.
• Ultraviolet rays have a higher frequency than
  violet light.
• Sun Rays
• Kills bacteria and other microorganisms

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X-Rays

• X-Rays have high energy and can penetrate matter.
• Used in medicine, industry and transportation to
  make pictures of the inside of a solid object.
• Wavelength of 12nm 0.005 nm

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Gamma Rays

• Gamma rays are the shortest wavelength (About
  0.005nm or less).
• They have the highest amount of energy.
• They are used in the medical field to kill cancer
  and take pictures of the brain, and in industrial
  situations as an inspection tool.

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Light and Materials

• Materials can be transparent, translucent or
  opaque.
• A transparent material transmits light, which
  means it allows most of the light that strikes it
  to pass through it.
• A translucent material scatters light. The
  object does not appear clear or distinct.
• An opaque material either absorbs or reflects all
  the light that strikes it.

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Interactions of Light

• When light strikes a new medium, the light can be
  reflected, absorbed, or transmitted. When light
  is transmitted, it can be refracted, polarized,
  or scattered.

• Reflection is the bouncing off of waves.
• An image is a copy of an object formed by
  reflected or refracted waves of light

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Types of Reflection

• Regular Reflection occurs when parallel light
  strike a surface and reflect all in the same
  direction.

• Diffuse reflection occurs when parallel light
  waves strike a rough, uneven surface, and reflect
  in many different directions.

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Refraction

• Lights waves refract, or bend, when it passes at
  an angle from one medium to another.
• A mirage is a false or distorted image caused by
  differences in temperature

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Polarization

• When light waves vibrate in only one plane the
  light is polarized.
• Used in sunglasses and in film

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Scattering

• Earths Atmosphere contains many molecules that
  scatter light.
• Scattering means that light is redirected as it
  passes through a medium.
• Why is the sky blue?

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White ROYGBV

• Sunlight is made up of all the colors of the
  visible spectrum.
• The process in which white light separates into
  colors is called dispersion.

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Color

• The color of an object depends on what the object
  is made of and on the color of light that strikes
  the object.
• The color reflected is the color you see. The
  colors absorbed are not visible.

• Primary colors are three specific colors that can
  be combined in varying amounts to create all
  possible colors. (Red, Green, Blue)
• Secondary colors are combinations of two primary
  colors. (Magenta, Cyan, Yellow)

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Color Wheel
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Mixing Pigments

• A pigment is a material that absorbs some colors
  of light and reflects other colors.
• The primary colors of pigments are cyan, magenta
  and yellow.
• Any two colors of pigments that combine to make
  black pigment are complementary colors of
  pigment.