Physics 535 Lectures Notes: 1 Sep 4Th 2007

Physics 249 introductory handout: Lecture 1, Sep 5th 2012 Reading: Chapter 3

Course: Physics 249 Fall 2012: A Modern Introduction to Physics MWF 9:55-10:45am 2223 Chamberlin Hall

Web site: 249 web site http://www.physics.wisc.edu/undergrads/courses/fall2012/249/

Faculty: Professor Matthew Herndon Office Hours: Wednesdays 11-12 Office: 4279 Chamberlin Hall Phone: (608) 262-8509 (office) Email: herndon at hep.wisc.edu

Teaching Assistant: Chien Seng Office Hours: Wednesdays 2:25pm, Thursdays 4:35 Email: cseng at wisc.edu Office: 5264 Chamberlin Hall

Text Book: Modern Physics 6th Edition Paul A. Tipler by Ralph Llewellyn Link: Modern Physics http://www.amazon.com/Modern-Physics-Paul-Tipler/dp/142925078X/ref=sr_1_11? s=books&ie=UTF8&qid=1345671086&sr=1-11 Web Site: Modern Physics 6e http://bcs.whfreeman.com/tiplermodernphysics6e/

Lectures: Covers concepts, derivation some example problems for complex topics. Lecture notes handed out in class and available on the course web site after each lecture.

Homework: Weekly homework except exam week. Homework due on Friday at the beginning of lecture. Generally covers material from proceeding Wednesday, Friday, and Monday lectures. First homework due Friday September 13th.

Discussion section and quizzes: Discussion sections: M 1:20-2:10pm, 2:25-3:15pm 2116 Chamberlin Hall Quizzes: Weekly quizzes given in discussion section except for exam week.

Exams: Two in class midterm exams and a final exam will be given. Midterm exams Friday Oct 12th and Friday Nov 16th Final exam Friday Dec. 21st 10:05-12:05

Grading: 30% Homework 10% Discussion Quizzes 30% Midterm exams 30% Final Exam

Honors: A 5 page (double spaced) term paper describing the work of a Nobel prize winner in physics is required for Honors credit. The paper should summarize the award winning work itself and present day research in the area including two recent papers from the ArXiv as well as references to the original research papers that resulted in the prize. Due Friday Dec. 7th. Please submit your paper by email in word or pdf format.

Syllabus topics. 1 Quantization of Charge Light and Energy 2 The Nuclear Atom 3 The Wavelike Properties of Particles 4 The Schrödinger Equation: 2 weeks Midterm Exam 1 5 Atomic Physics: 2 weeks 6 Statistical Physics 7 Molecular Structure and Spectra 8 Nuclear Physics Midterm exam 2 10 Review of Relativity 11 Particle physics: 3 weeks

The idea of particles as discrete entities with quantized charges seem obvious today to anyone who has learned some basic physics. We understand that the atom is composed of protons and neutrons in a compact nucleus with and orbiting electrons. We know that the electrons have one unit of negative electric charge while the protons have one unit of positive electric charge. The idea of discrete matter particles can be extended to photons, which carry a quantized amount of energy.

However these ideas were revolutionary at the time and they bring up questions that require an extensive introduction to modern physics to understand. Even today fundamental questions that are brought up by the ideas of quantization as explained by Quantum Mechanics are not understood. An example of a question we have an answer to is why does the discrete or quantized particle, the photon, exist. Though fully answering this question takes the full framework of particle physics, which is based on a version of quantum mechanics that obeys Einstein’s theory of relativity.

An example of a set of questions we don’t have an answer to is why the electron has the exact value of electric charge that it has and why does the proton have an equal magnitude but opposite charge. This question is actually made more difficult by particle physics which has shown that the proton is made up of three particles called quarks with charges -1/3e 2/3e and 2/3e.

In this class we will examine the experimental discoveries that led to the theory of quantum mechanics. We will then solve the equations of quantum mechanics in order to understand the physics of atoms and molecules. Finally we will expand the ideas of quantum mechanics to include relativity and study nuclear and particle physics. This will take us on a journey that starts with the paradigm shifts that fundamentally revised our understanding of physics (Quantum Mechanics and Relativity) and takes us to the forefront of modern research on those subjects.

We will go from the ideas of classical physics, which covered macroscopic and slow moving physics, to Quantum Mechanics, which explains microscopic physics, relativity, which explains physics near or at the speed of light, to particle physics, which explains microscopic physics near or at the speed of light.

Understanding of physics in ~1850 1) Forces: We understood the ideas of forces as defined by Newton’s laws. Also we understood the ideas of forces acting as a distance as in Newton’s theory of gravitation. We didn’t understand why actions at a distance should take place.

2) Electricity and magnetism. We newly understood another force that acted at a distance. Maxwell’s theory of electricity and magnetics as explained by Maxwell’s equations. We didn’t understand the source of electric or magnetic fields.

1 and 2 covered much of the ideas we classify as classical physics.

3) Matter: We understood that matter probably made up of fundamental building blocks typically called atoms (or molecules). Thus matter was discrete on the microscopic scale. However, these discrete atoms had not been directly observed. Rather they were inferred from evidence that gasses acted in a way consistent with being composed of discrete small solid objects. Note that the study of thermodynamics and statistical phenomena was key in understanding a fundamental property of microscopic matter. The exact structure of these discrete atoms was not understood. 4) We understood that a solution of Maxwell’s equations existed in which oscillating electric and magnetic fields could reinforce each other and travel through space at a constant speed (the wave solution for light). Evidently no source need in this case.

We were already seeing hints of non classical physics but did not understand them yet.

Given these tools we had a framework to understand the results of some very surprising experiments in a quantitative way and start to develop answers to the questions posed by those results and what had been understood up to that point.