The document discusses key concepts in the development of quantum theory including: 1) De Broglie hypothesized that particles like electrons exhibit wave-like properties and can have an associated wavelength. 2) Schrodinger used de Broglie's idea to develop the first quantum theory based on wave equations to describe electrons rather than classical orbits. 3) Heisenberg formulated the uncertainty principle - that the exact position and momentum of a particle cannot be known simultaneously. 4) Experiments on the photoelectric effect showed photons eject electrons from metals immediately, contradicting classical wave theory but supporting a particle-like nature for photons.

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