PHZ3400-09 Modern Physics

Ah, the reason we all majored in physics in the first place...

These lectures were given by Dr. Vald's friend/colleague.

At the end of the 19th century, scientists had gotten a lot done. But there was no explanation for things that happened at the Quantum level. What happened when things got very small and very fast?

Black Body Radiation

• Blackbody absorbs / not emits light
• Stefan Boltzmann Law I = sigma T^4
• Wien's Law lambda T = b
• Blackbody Radition Spectrum: UV catastrophe

Classical physics does not explain that

• This led to Planck's Hypothesis

Planck's Hypothesis

• radition comes from eletric oscillators
• energy of each mode of oscillation is quantized E = n h v
• Energy can be emitted or absorbed

Specific Heat of Solids

• Cv / Na = const
• Cv = 3 Na K from classical physics
• But at low temperatures C drops sharply and approaches zero
• Phonons: quantization of lattice vibrations

Photoelectric Effect

• Einstein got a nobel prize for this instead of relativity
• Apparatus measure the number of photoelectrons and the maximum Kinetic energy
• Observations not explained by classical wave theory of light

i. Increasing intensity of light increases the number of photoelectrons but not the maximum KE
ii Red light emits no electrons independent of intensity
iii.

Particle-Wave Duality and de Broglie Wavelength

• de Broglie Hypothesis
• everything in nature has both wave and particle nature
• lambda = h / p
• Davidsson Germer experiment
• Thompson Reid experiment

Heisenberg's Uncertainty Principle

• x p > h bar
• t E > h bar
• Measurement always disturbs object
• Deterministric view of nature is fundamentally flawed

Atomic Spectra

• Spectra Lines and Atomic Spectra
• Plum Pudding model of atom
• Rutherford's scattering experiment
• Planetary model contradicts experiments

i. Stability of matter
ii. Atomic Spectra lines

• Bohr's Model 1913 basic hypothesis

i. Electrons in atoms follow classical physics and Rutherford's atomic model
ii. blah blah
iii. blah blah

• Bohr's theory applied to hydrogen like atoms

yadda yadda

• Line Spectra Rydberg's

Atomic Shell Structure

• quantum numbers (principal, orbital, magnetic, spin)
• Selectron rule in quantum transitions N = +- 1
• Electron configurations
• Pauli expclusion principle
• Periodic table

Schroedinger Equation

• Describes many things but not waves at a very high energy