Electromagnetic Radiation

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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

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Electromagnetic Radiation
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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

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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

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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

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Electromagnetic Radiation

• Radio antennas
• AM and FM radio

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Electromagnetic Radiation

• Earths seasons

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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

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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

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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?