Electromagnetic Spectrum

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Electromagnetic Spectrum
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EMS

• Made up of electromagnetic radiation
• Form of energy
• Behaves like a wave

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Kinds of radiation are

• Gamma Rays
• X Rays
• Ultraviolet Rays
• VISIBLE LIGHT
• Infrared
• Microwave
• Radio Waves

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Features of Waves

• Have repetitive motion
• Characterized by four properties
• Wavelength
• Frequency
• Amplitude
• Speed

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Wavelength (?)

• One full cycle of a wave
• Crest to Crest or Trough to Trough
• Wavelengths of visible light are 400 750
  nanometers
• Violet Light short wavelength
• high frequency
• Red Light long wavelength
• low frequency

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Frequency (v)

• The number of cycles (one upward and downward
  motion) a wave completes in one second.
• Speed of light is a constant (c)
• Speed 3.0 x 108 meters per second
• (in air)
• Waves travel slower through other types of matter

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Amplitude

• Height of a wave
• Measured from origin to peak

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Relationship between (? and v)

• C ( ? ) x (v)
• Where
• c speed of light
• ? wavelength
• v frequency

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• Since the speed of light is constant, wavelength
  frequency have a constant relationship
• They are inversely proportional
• As wavelength of light decreases, the frequency
  of light increases
• As wavelength of light increases, the frequency
  of light decreases

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How are Energy Frequency Related?

• They are directly proportional
• As frequency increases, energy increases
• As frequency decreases, energy decreases

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The Photoelectric Effect

• Emission of electrons from a metal when light
  shines on the metal
• Wave Theory says that light of any frequency
  should be capable of supplying enough energy to
  loosen an electron
• THIS WAS NOT THE CASE
• There was a minimum frequency that had to be met
  before the photoelectric effect would occur

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Albert Einstein

• 1905 Electromagnetic Radiation has a dual wave
  particle existence
• A particle of electromagnetic radiation (light)
  with zero mass and a quantum of energy is called
  a photon

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Hypothesis

• Light could be a wave
• Light could be a stream of particles
• Photon particle of radiation
• has no mass
• carries a quantum of energy
• E photon (h) x (v)
• This won Einstein his only Nobel Prize

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Can electrons act as a particle and a wave???

• French Scientist Louis de Broglie
• Discovered that electrons have a similar amount
  of energy as a photon

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German Physicist Max Planck discovered

• Objects emit energy in small, specific amounts
  called quanta
• Quantum minimum quantity of energy that can be
  lost or gained by an electron
• (His work proved Einstein correct)
• E h x v
• E energy
• h Plancks constant (6.626E-34 Js)
• v frequency of radiation

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20th Century

• Atomic Theory
• Neils Bohrs theory involved absorption and
  emission of light
• When an electron jumped to a higher energy level,
  it absorbed energy
• When an electron returned to a lower energy level
  it gave off energy in the form of light