Introduction to Electromagnetism

1
Electrons as waves (1923)
DeBroglie postulated if light can behave like a
particle (E hc/l pc) then maybe matter could
behave like waves! What would be an electrons
wavelength? h/l p mv Integer wavelengths
circumference nl 2pr mv L mvr
Quantization of angular momentum!
(1927) Davisson and Germer discovered that
electrons can diffract as waves! thanks to an
accident with their nickel crystal.
2
Bohr model for the Hydrogen atom
Solve for (1) v2 Quantize angular momentum
mvr nh/2p using deBroglie l Solve for (2)
v2 Equate v2v2 Solve for r
3
Energy levels of Bohr atom

• Calculate H energy levels from theory
• Compare to energies of observed spectral lines
• They match!

4
Quantum synthesis Bohr deBroglie

• Bohr used Rutherfords model of the orbiting
  electron and Plancks quantum applied to angular
  momentum, later justified by deBroglies
  hypothesis of electron wavelengths
• angular momentum is quantized in electron orbits
• orbit radii and energy levels are derived for
  H-like atoms.
• Despite unanswered questions (such as how could
  such orbits be stable?), Bohrs model fit
  observations
• Balmer spectrum Rydberg constant