Modern Physics Sixth Edition

Book Preface

In preparing this new edition of Modern Physics, we have again relied heavily on the many helpful suggestions from a large team of reviewers and from a host of instructor and student users of the earlier editions. Their advice reflected the discoveries that have further enlarged modern physics in the first decade of the new century, took note of the evolution that is occurring in the teaching of physics in colleges and universities, and recognized the growing role of modern physics in the biological sciences. As the term modern physics has come to mean the physics of the modern era—relativity and quantum theory—we have heeded the advice of many users and reviewers and preserved the historical and cultural flavor of the book while being careful to maintain the mathematical level of the earlier editions. We continue to provide the flexibility for instructors to match the book and its supporting ancillaries to a wide variety of teaching modes, including both one- and two-semester courses and media-enhanced courses.

New and Enhanced Features

The successful features of the earlier editions have been retained, many have been augmented, and new ones have been added. Among them are the following:
• The logical structure—beginning with an introduction to relativity and quantization and following with applications—has been continued. Opening the book with relativity has been endorsed by many reviewers and instructors.
• As in the earlier editions, the end-of-chapter problems are separated into three sets based on difficulty, the least difficult also grouped by chapter section.
New problems have been added in every chapter as we continue to offer more problems than any other book in the field.
• The first edition’s Instructors’ Solutions Manual with solutions, not just answers, to all end-of-chapter problems was the first such aid to accompany a physics (and not just a modern physics) textbook, and that leadership has been continued in this edition. The Instructors’ Solutions Manual (ISM) is available in print or on CD for those adopting Modern Physics, sixth edition, for their classes. As with the previous editions, the popular paperback Student’s Solution Manual, containing one-quarter of the solutions in the ISM, is also available.
• We have continued to include many worked-out examples in every chapter, a feature singled out by many instructors as a strength of the book. Several new examples at the interface between modern physics and the biological sciences have been added. As before, we frequently use combined quantities such as hc, Uc, and ke2 in eV # nm to simplify many numerical calculations.
• The summaries and reference lists at the end of every chapter have, of course, been retained and augmented, including the two-column format of the summaries that improves their clarity.

• We have continued the use of real data in figures, photos of real people and apparatus, and short quotations by many scientists who were key participants in the development of modern physics. These features, along with the Notes at the end of each chapter, bring to life many events in the history of science and help counter the too-prevalent view among students that physics is a dull, impersonal collection of facts and formulas.
• More than two dozen Exploring sections, identified by an atom icon and dealing with text-related topics that captivate student interest such as superluminal speed, giant atoms, and spintronics, are distributed throughout the text.
• The book’s Web site includes 31 More sections, which expand in depth on many text-related topics. These have been enthusiastically endorsed by both students and instructors and often serve as springboards for projects and alternate credit assignments. Identified by an icon CCR , each is introduced with a brief text box.
• More than 125 questions intended to foster discussion and review of concepts are distributed throughout the book, including several new ones in this edition. These have received numerous positive comments from many instructors over the years, often citing how the questions encourage deeper thought about the topic.
• A number of new Application Notes have been added to the sixth edition. These brief notes in the margins of many pages point to a few of the many benefits to society that have been made possible by a discovery or development in modern physics.
• Also new in the sixth edition are the For You text boxes. These text boxes highlight current and future research and development activity toward which today’s students may consider directing their own career interests.
• Recognizing the need for students on occasion to be able to quickly review key concepts from classical physics that relate to topics developed in modern physics, the Classical Concept Review (CCR) was introduced in the book’s fifth edition.

Found on the book’s Web site and identified by a numbered icon CCR in the margin near the pertinent modern physics discussion, the CCR can be printed out to provide a convenient study-support booklet. Several new CCRs have been added to the sixth edition. The CCRs provide concise reviews of pertinent classical concepts just a mouse click away.

Organization and Coverage

This edition, like the earlier editions, is divided into two parts: Part 1, “Relativity and Quantum Mechanics: The Foundations of Modern Physics,” and Part 2, “Applications of Quantum Mechanics and Relativity.” We continue to open Part 1 with the two relativity chapters. This location for relativity is firmly endorsed by users and reviewers. The rationale is that this arrangement avoids separation of the foundations of quantum mechanics in Chapters 3 through 8 from its applications in Chapters 9 through 12. The two-chapter format for relativity provides instructors the flexibility to cover only the basic concepts or to go deeper into the subject. Chapter 1 covers the essentials of special relativity and includes discussions of several paradoxes, such as the twin paradox and the pole-in-the-barn paradox, that never fail to excite student interest. Relativistic energy and momentum are covered in Chapter 2, which concludes with a mostly qualitative section on general relativity that emphasizes experimental tests. Many instructors use this section as an opener for Chapter 13, Astrophysics and Cosmology. Since the relation E2  p2c2 1 (mc2)2 is the result most needed for the later applications chapters, it is possible to omit Chapter 2 without disturbing continuity.

Chapters 1 through 8 have been updated with several improved explanations and new diagrams. Many quantitative topics are included as More sections on the Web site. Examples of these topics are the derivation of Compton’s equation (Chapter 3), the details of Rutherford’s alpha-scattering theory (Chapter 4), the graphical solution of the finite square well (Chapter 6), and the excited states and spectra of two electron atoms (Chapter 7). The comparisons of classical and quantum statistics are illustrated with several examples in Chapter 8, and, unlike the other chapters in Part 1, it is arranged to be covered briefly and qualitatively, if desired. This chapter, like Chapter 2, is not essential to the understanding of the applications chapters of Part 2 and may be used as an application chapter or omitted without loss of continuity.

Preserving the approach used in the previous edition, in Part 2 the ideas and methods discussed in Part 1 are applied to the study of molecules, solids, nuclei, particles, and the cosmos. Also in Part 2 several explanations have been improved and new diagrams added. Chapter 9 (Molecular Structure and Spectra) is a broad, detailed discussion of molecular bonding and the basic types of lasers. Chapter 10 (Solid State Physics) includes sections on bonding in metals, magnetism, and superconductivity. Chapter 11 (Nuclear Physics) is an integration of the nuclear theory and applications. It focuses on nuclear structure and properties, radioactivity, and the applications of nuclear reactions. Included in the last topic are fission, fusion, and several techniques of age dating and elemental analysis. The material on nuclear power and the discussion of radiation dosage continue as More sections. Chapter 12 (Particle Physics) was substantially reorganized and rewritten with a focus on the Standard Model in the fifth edition and has been revised for the sixth edition to reflect the recent advances of that field. The emphasis is on the fundamental interactions of quarks, leptons, and force carriers and includes discussions of the conservation laws, neutrino oscillations, and supersymmetry. Finally, Chapter 13 (Astrophysics and Cosmology) examines the current observations of stars and galaxies and qualitatively integrates our discussions of quantum mechanics, atoms, nuclei, particles, and relativity to explain our present understanding of the origin and evolution of the universe from the Big Bang to dark energy and to highlight the enormity of what is not yet known.