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To review Rutherford’s model of the atom To explore the nature of electromagnetic radiation To see how atoms emit ligh

Objectives. To review Rutherford’s model of the atom To explore the nature of electromagnetic radiation To see how atoms emit light . A. Rutherford’s Atom . …….but there is a problem here!! . When were you last exposed to electromagnetic radiation?. B. Energy and Light .

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To review Rutherford’s model of the atom To explore the nature of electromagnetic radiation To see how atoms emit ligh

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  1. Objectives • To review Rutherford’s model of the atom • To explore the nature of electromagnetic radiation • To see how atoms emit light

  2. A. Rutherford’s Atom …….but there is a problem here!!

  3. When were you last exposed to electromagnetic radiation?

  4. B. Energy and Light • What is the nature of electromagnetic radiation? • How are the types of electromagnetic radiation different? • Light can be modeled as a wave, like a wave in water

  5. B. Energy and Light • How are the types of light different? c = ν.λ (m) • Wavelength, λ (Greek letter “lambda”) units - m • Frequency, ν (Greek letter “nu”) units - s-1 or Hertz (Hz) • Amplitude, peak height – relates to energy in wave • Speed, c : velocity of light in a vacuum is 3x108 m.s-1 ν (s-1)

  6. B. Energy and Light • Electromagnetic radiation

  7. Wavelength and Frequency of Visible Light Frequency in Terahertz (1THz = 1012 Hz) and Wavelength in Nanometers (1nm = 10-9 meters)

  8. Light Sometimes Behaves in Un-wavelike Ways • The Photoelectric Effect • Light shining on a metal surface can cause electrons to be separated from their atoms • Below a threshold frequency no electrons are emitted however high the intensity • At the threshold frequency electrons start to be emitted • At higher frequencies electrons have additional kinetic energy

  9. B. Energy and Light • Dual nature of light – Two co-existing models • Wave • Photon – packet of energy

  10. B. Energy and Light • Different photons (from light of different wavelengths) carry different amounts of energy. Energy of photon = h.ν (h is Planck’s Constant )

  11. C. Emission of Energy by Atoms • Atoms can give off light • They first must receive energy and become excited. • The energy is released in the form of a photon.

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