PHZ3400-09 Modern Physics

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

Group 3 is the best

Modern Physics Picture of an Atom Header Bold Text Italic text Bold Italics Normal Text

Modern Physics is [Insert Definition Here]

Introduction

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

# Increasing intensity of light increases the number of photoelectrons but not the maximum KE
# Red light emits no electrons independent of intensity
#

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

# Stability of matter
# Atomic Spectra lines

• Bohr's Model 1913 basic hypothesis

# Electrons in atoms follow classical physics and Rutherford's atomic model
# blah blah
# 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