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EM Spectrum, de Broglie, PE Notes


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EM Spectrum, de Broglie, PE Notes

  1. 1. de Broglie Wavelength
  2. 2. de Broglie• Pictured the electron in its circular orbit as a particle wave• Can produce "standing waves" under resonant conditions• Developed the idea that a particle with mass, m, and a velocity, v, has a wavelength associated with it => de Broglie Wavelength
  3. 3. de Broglie
  4. 4. de Broglie
  5. 5. de Broglie
  6. 6. Schrödinger• Used de Broglie wavelength to create a quantum theory based on waves• Did not keep the "orbits"• The wave/particle model cannot determine the location and momentum of an electron at the same time• The quantum model predicts the probability that an e- is at a specific location
  7. 7. Heisenberg Uncertainty Principle• Can only determine the location or the momentum (velocity) of the particle - not both at the same time!
  8. 8. Photons and Photoelectric Effect
  9. 9. Photoelectric Effect• Metal is illuminated by electromagnetic radiation• Energy that is absorbed near the surface can free electrons, causing es to fly off• Released electrons are called photoelectrons
  10. 10. Wave theory predicts the following:• Significant time delay between the illumination and ejection - build up of KE to free e-s• Increasing the intensity of light = cause electrons to leave with greater KE• Photoelectrons would be released regardless of frequency of light, as long as the intensity was great enough.... But these are FALSE!
  11. 11. Photoelectric Effect Findings• Photons were ejected immediately• Increasing the intensity did not change the KE although more e-s were ejected, KE does not increase.• If the frequency fell below a threshold (specific for each metal), no photoelectrons would be ejected, regardless of intensity!• If the frequency increases above the threshold, KE increases linearly
  12. 12. PE Effect - Math• Threshold Frequency• Work Function - the minimum amount of energy required on a metal surface to eject an electron• How are these two related?
  13. 13. PE Effect - Math
  14. 14. Photoelectric Effect