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Physics 305

PHYS 305

Catalog Entry

PHYS 305. Modern Physics
Three hours lecture; two hours laboratory (4).

Prerequisite: PHYS 112 or 222.

Introduction to modern physics, including special relativity, quantum theory, atomic and nuclear physics, elementary particles.


Detailed Description of Content of Course

Although the title "modern physics" may seem somewhat nonspecific, the topics generally covered in a course with this title have become fairly standardized. We begin with a substantial treatment of special relativity. Here, as with all topics covered in this course, the empirical foundations are emphasized. Furthermore, the history of the development of the subject and some discussion of the personalities of the people involved in this development are not omitted. The kinematical and dynamical effects of special relativity are then discussed quantitatively, and the student is expected to solve problems using the Lorentz transformation or the relativistic expressions for momentum and energy. This occupies the first quarter of the class. We then discuss the roots of quantum physics and that body of inspired ad hoc prescriptions which has become known as the "old quantum theory." Included here are Planck's formula for blackbody radiation, Einstein's explanation of the photoelectric effect, and Bohr's atomic model. The postulate of de Broglie bridges the gap between the old quantum theory and the quantum mechanics of Heisenberg and Schroedinger. We consider applications of Schroedinger's wave mechanics to simple systems, including the hydrogen atom. The course then concludes with an elementary, mostly descriptive, treatment of atomic, nuclear, and particle physics.

In summary, the topics covered are:

1. Special theory of relativity
2. Blackbody radiation
3. Photoelectric effect, Compton effect
4. Bohr model
5. De Broglie's postulate
6. Heisenberg uncertainty principle
7. Schroedinger's wave mechanics
8. Atomic physics, spin, the exclusion principle
9. Nuclear physics: binding energy, energy balance in nuclear reactions, radioactivity 10. Particle spectroscopy (descriptive)


Detailed Description of Conduct of Course

The material presented in this course challenges many of the preconceptions about space, time, and matter which are derived from everyday experiences. This tends to draw questions, comments, and expressions of disbelief from even the most reticent students. This behavior is encouraged and lecture periods often include a large amount of time devoted to discussion or to the instructor's response to students' questions. More so than in other physics courses, PHYS 410 requires discussion of ideas. However, in physics, a good idea is ultimately a quantitative idea. Therefore, much time must also be devoted to problem solving. Examples are presented and solved in detail, with extensive commentary about motivations and procedures. The students are then encouraged to work as many problems as possible at home.

Lab exercises are included when appropriate. Since some of the material does not lend itself to experimentation at the level for which Radford University is equipped, whereas other labs may extend over multiple lab periods, flexibility in lab scheduling is desirable. Normally, no more than approximately seven different experiments would be performed during the semester. Some of the experiments, however, may require more than two hours of lab time.


Goals and Objectives of Course

1. Students are introduced to some of the results of modern physics and obtain an appreciation of the remarkable changes that have occurred in the understanding of space, time, and matter.
2. Students are expected to be able to solve basic problems in relativity and elementary quantum theory, including applications to atomic, nuclear, and particle physics.
3. Students are expected to gain some appreciation of the history of the subject, the people involved, and applications of the results to society and technology. The social and technological aspects occur naturally during the discussion of certain subjects, e.g., nuclear fission.
4. Through the lab work, students are able to see for themselves some of the effects discussed in class.

They are expected to develop experimental skills at a higher level than those required in the elementary physics sequences.


Assessment Measures

The experimental skills are evaluated through observation and discussion in lab, and through submitted lab reports. Classroom participation and conversation with students outside the class help to gauge their understanding of the ideas of modern physics and their appreciation of the history, people, and cultural impact of the subject. Their quantitative understanding is measured through homework problems, tests, and the final exam.


Other Course Information

Students taking this course for graduate credit have two options. They may either: (1) demonstrate a level of proficiency with the material beyond that of the undergraduate students, or (2) submit a library research paper on a topic related to the course material. In the first case, additional homework problems, including problems of greater complexity, will be assigned; in addition, one of the problems on each test and the exam will be replaced by a more sophisticated problem. In the second case, the topic of the paper, its length, and its expected level of scientific maturity will be discussed with the instructor at the beginning of the semester.



September 2001 Reviewed by Walter S. Jaronski, Chair