The Electromagnetic Theory

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The Electromagnetic Theory
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Michael Faraday (1791-1867)

• Hot objects transfer heat energy by radiation
• If temperature is high enough, object also
  radiate light
• If light source is blocked so is the heating
  effect

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• Sun and clouds are an example
• Faraday was investigating the attraction and
  repulsion of electrically charged bodies
• Faraday developed a model including heat, light
  and electricity

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James Clerk Maxwell

• By 1865 Maxwell (Scottish mathematical physicist)
  developed a set of mathematical equations that
  predicted heat, light and electricity all moved
  through space at the speed of light as
  electromagnetic disturbances

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• The electromagnetic theory brought together heat,
  light and electricity. Maxwell determined that
  the energy of an electromagnetic wave is equally
  divided between an electric field and a magnetic
  field

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Heinrich Rudolf Hertz

• By 1885, German physicist confirmed the
  electromagnetic theory by experimentation

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The Electromagnetic Spectrum

• Electromagnetic energy can only be detected and
  measured when it is intercepted by matter and
  changed into other forms of energy
• thermal, electric, kinetic

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• The range of radiation frequencies extends from
  about 10 Hz to 1025 Hz.
• All electromagnetic radiation travel at the speed
  of light

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• The spectrum is separated into 8 major regions
• The visible spectrum is the smallest region
• Light is defined as radiant energy that a human
  can see

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Wave Theory is a Certainty!

• Many physicists felt that at this time all
  significant laws of physics had been discovered.
• There is little left to do other than develop new
  and more sophisticated techniques for measuring.

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• Hertz stated, The wave theory of light is from
  the point of view of human beings, a certainty.

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The Sixth Property

• Oddly enough Hertz soon discovered the fact that
  light energy is absorbed and now the wave theory
  couldnt explain all properties of light.

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New Physics

• The stage is now set for the new physics that
  emerged in the early year of the twentieth
  century.
• Maybe Newton was correct after all.