3. de Broglie Wavelength

4. 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

5. de Broglie

6. de Broglie

7. de Broglie

8. 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

9. Heisenberg Uncertainty Principle
• Can only determine the
location or the momentum
(velocity) of the particle - not
both at the same time!

11. Photons and Photoelectric Effect

12. Photoelectric Effect
• Metal is illuminated by electromagnetic
radiation
• Energy that is absorbed near the surface can
free electrons, causing e's to fly off
• Released electrons are called photoelectrons

13. 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!

14. 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

16. 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?

17. PE Effect - Math

18. Photoelectric Effect