Ph 311,312: Introduction to Modern Physics Ph 311,312: Introduction to Modern Physics

Course instructor: R. Egerton, Department of Physics


EgertonR@pdx.edu, phone 725-4227

Classical physics implies discoveries made during the 19th century and earlier.

Mechanics was established through experiments of Galileo and formulated by Newton, who introduced the concepts of force F ("action at a distance") and mass m. Newton also introduced a formula (F = G m1 m2 / r^2) for the universal gravitational force, whose proportionality constant G was first measured by Cavendish,

Electromagnetism represents a combination of the classical theories of electrostatics, electricity and magnetism. Maxwell's Equations show that electromagnetic travelling waves, travelling in vacuum, have a speed equal to the measured speed of light. This speed is independent of wavelength, so other forms of electromagnetic radiation have similar properties. Since other forms of wave motion (sound, water waves etc.) require a medium in which to propagate, a (luminiferous) ether was assumed to be present everywhere in the universe. (The ether can also be thought of as "explaining" action at a distance for electrostatic and magnetic forces; Descartes believed that a vortex in the ether caused the motion of planets around the sun).

Optics was developed by Newton, Hooke and Huygens (mid-17th century) and by Fresnel and Young (in the early 1800's). Geometrical optics assumes that light travels (in a uniform medium) in straight lines, like a stream of particles (Newton's corpuscles of light). However, diffraction effects occur when light is intercepted by objects of small dimensions, and can only by explained by physical optics - taking light to be a wave.

Classical physics also includes the study of heat (thermodynamics) and of fluids.



Modern physics is built upon the theories of relativity and of quantum physics. In 1905, Einstein introduced his Special Theory of Relativity; later he introduced the General Theory, which provides a "geometrical" explanation of gravity.
Quantum theory started at the end of the 19th century, from attempts to explain the intensity distribution of blackbody radiation emitted from heated objects. In order to explain details of the photoelectric effect, Einstein introduced (also in 1905) the idea that light (and other forms of electromagnetic radiation) must sometimes be regarded as packets of energy (quanta or photons). Further evidence for this idea comes from certain properties of x-rays and observations of the creation and annihilation of elementary particles.

In 1923, De Broglie introduced the idea of matter waves, soon verified by the discovery of the diffraction properties of particles. The Rutherford planetary model of the atom gave way to Bohr's quantum model and later to a wave description of the atomic electrons based on wave mechanics, developed by Schrodinger and others in the 1920's.



Achievements of quantum physics include a detailed explanation of how atoms interact via their outer-shell electrons (quantum chemistry), properties of the atomic nucleus (nuclear physics) and of elementary particles (particle physics), which have been tested and further developed by experiments made using particle accelerators. and a detailed account of the physical properties of solids (solid state physics). Combining particle physics with the theories of Relativity provides our modern account of the structure of the universe as a whole and its evolution (cosmology).


Books for Ph 311 and Ph 312 :

Required:

Modern Physics, by R.A. Serway, C.J. Moses and C.A. Moyer (Saunders College Publishing: second edition)

Optional reading:

From Quarks to the Cosmos, by Leon M. Ledermann and David N. Schramm (1995, Freeman and Co. paperback)

The Rise of the New Physics, by A. D'Abro (1939, Dover, 982 pages) Includes mathematical principles, maybe too advanced for this course.

The Dancing Wu Li Masters, by G. Zukav (1979, Bantam, 337 pages) New-age account of Relativity, Quantum and Particle Physics.

Dreams of a Final Theory, by S. Weinberg (1992, Vintage/Random House) Particle-physicist's account of the quest for a unifying theory of nature.


Ph 311 course assignments (with answers):

Consequences of Special Relativity

Relativistic Energy

Blackbody Radiation and Photoelectric Effect

Compton Effect and Pair Annihilation

Rutherford and Bohr Models

Mid-Term Test (October 1999)

Final Exam (December 1999)


Ph 312 course assignments (with answers):

De Broglie waves, electron diffraction

Heisenberg Uncertainty Principle

Schroedinger Equation

Nuclear Physics

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Mid-Term Test (2000)

Final Exam (2000)