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Electromagnetic Radiation

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Electromagnetic Radiation The Electromagnetic Spectrum The range of electromagnetic waves which includes visible light. Wavelength Frequency Energy – PowerPoint PPT presentation

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Title: Electromagnetic Radiation


1
Electromagnetic Radiation
  • The Electromagnetic Spectrum
  • The range of electromagnetic waves which
    includes visible light.
  • Wavelength
  • Frequency
  • Energy
  • All EM waves travel at the same speed in a
    vacuum
  • 300,000,000 m/s

2
Electromagnetic Radiation
3
Electromagnetic Radiation
  • Electromagnetic Waves
  • Waves due to varying electric and magnetic
    fields of moving charges
  • ?E ? ?B ? ?E
  • They are transverse
  • E and B have the same frequency and are in phase
    with each other

4
Electromagnetic Radiation
  • Calculating the speed of light
  • James Clerk Maxwell (1864) publishes four laws
    that govern electromagnetic phenomena
  • He was able to calculate the theoretical speed
    of EM waves
  • The calculated and observed values for the speed
    of EM waves matched
  • Heinrich Hertz (1888) proved that EM waves exist

5
Electromagnetic Radiation
  • Radio antennas
  • A generator oscillates the charges in the
    antenna and produces a varying electric field
    which produces a varying magnetic field and

6
Electromagnetic Radiation
  • Radio antennas
  • AM and FM radio

7
Electromagnetic Radiation
  • Earths seasons

8
Electromagnetic Radiation
  • How EM waves travel through matter
  • Atoms vary in the bonding strength with their
    electrons which means their natural frequencies
    are different as well
  • Glass is transparent to visible light but not to
    UV or IR
  • Resonance
  • Greenhouses and global warming
  • Light does slow down as it travels due to the
    re-emissions of the atoms in the material

9
Electromagnetic Radiation
  • Polarization
  • The electric field is limited to one plane of
    motion
  • Filters select which electric field orientations
    will pass through
  • Sunglasses
  • LCDs
  • Applications

10
Electromagnetic Radiation
  • Scattering of light
  • Absorption and re-emission of light by electrons
  • Why is the sky blue?
  • Why is the Sun yellow?
  • Why is a sunset red?
  • Why are clouds white?
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