文档介绍：What is Modern Physics?
Modern physics only came of age in the 1900’s.
Physicists discovered that Newtonian mechanics did not apply when objects were very small or moved very fast!
If things are confined to very small dimensions (nanometer-scale), then QUANTUM mechanics is necessary.
Atomic orbitals, quantum heterostructures.
If things move very fast (close to the speed of light), then RELATIVISTIC mechanics is necessary.
Cosmic particles, atomic clocks (GPS), synchrotrons.
Plan for Physics 320.
Test #1: Nuclear Atom, Wave/Particle Duality, Wave Packets
Test #2: Schroedinger Equation, Atomic & Solid-state Physics
Nuclear Physics, Relativity
Phys 320 - Baski
Topic 1: Nuclear Atomic Model
Topic 1: Nuclear Atomic Model
Optical (Atomic) Spectra
Lower-energy optical absorption/emission lines from materials indicate quantized electron energy levels.
Bohr model predicts energy transitions for one-electron atoms.
X-ray Spectra
Analogous to optical spectra, but for higher-energy x-ray transitions of heavier, multi-electron elements.
Franck-Hertz Experiment
Quantized inelastic scattering of electrons in Hg gas provide evidence for atomic energy levels.
Rutherford Scattering Experiment
Large scattering angles of alpha particles from atoms in a metal foil indicate a “hard” nuclear model.
Phys 320 - Baski
Topic 1: Nuclear Atomic Model
Atomic Spectra
In 1885, Balmer observed Hydrogen spectrum and saw colored lines.
Found empirical formula for discrete wavelengths of lines.
Formula generalized by Rydberg for all one-electron atoms.
Prism separates wavelengths
Q: Where is Red vs. Blue line?
Phys 320 - Baski
Topic 1: Nuclear Atomic Model
Atomic Spectra: Modern Physics Lab
Neon Tube
Diffraction
Grating
(to separate light)
Eyepiece
(to observe lines)
High Voltage
Supply
(to “excite” atoms)
Phys 320 - Baski
Topic 1: Nuclear Atomic Model
Atomic Spectra: Hydrogen Energy Levels
Lyman Series
(ultraviolet)
Balmer Series
(visible)
Paschen Series
(IR)
Lyman
Balmer