3637_CassidyTX_00fm 6/19/02 12:08 PM Page i UNDERSTANDING PHYSICS Series Editors John P. Ertel Robert C. Hilborn David Peak Thomas Rossing Cindy Schwarz 3637_CassidyTX_00fm 6/19/02 12:08 PM Page ii UNDERGRADUATE TEXTS IN CONTEMPORARY PHYSICS Cassidy, Holton, and Rutherford, Understanding Physics Enns and McGuire, Computer Algebra Recipes: AGourmet’s Guide to the Mathematical Models of Science Hassani, Mathematical Methods: For Students of Physics and Related Fields Holbrow, Lloyd, and Amato, Modern Introductory Physics Roe, Probability and Statistics in Experimental Physics, Second Edition Rossing and Chiaverina, Light Science: Physics and the Visual Arts 3637_CassidyTX_00fm 6/19/02 12:08 PM Page iii UNDERSTANDING PHYSICS David Cassidy Gerald Holton James Rutherford With 571 Illustrations, with 6 in Full Color 123 3637_CassidyTX_00fm 6/19/02 12:08 PM Page iv David Cassidy Gerald Holton Professor of Natural Science Mallinckrodt Professor of Physics and History Natural Science Program of Science, Emeritus Hofstra University 358 Jefferson Physical Laboratory Hempstead, NY 11549 Harvard University USA Cambridge, MA 02138 [email protected] USA James Rutherford Education Advisor American Association for Advancement of Science Washington, DC 20005 USA Series Editors John P. Ertel Robert C. Hilborn Cindy Schwarz Department of Physics Department of Physics Department of Physics and United States Naval Academy Amherst College Astronomy 572 Holloway Road Amherst, MA 01002 Vassar College Annapolis, MD 21402-5026 USA Poughkeepsie, NY 12601 USA [email protected] USA [email protected] [email protected] David Peak Thomas Rossing Department of Physics Department of Physics Utah State University Northern Illinois University Logan, UT 84322 De Kalb, IL 60115 USA USA [email protected] [email protected] Library of Congress Cataloging-in-Publication Data Cassidy, David C., 1945– Understanding physics / David Cassidy,Gerald Holton, F. James Rutherford. p. cm. — (Undergraduate texts in contemporary physics) Rev. ed. of: The project physics course. 1971. Includes bibliographical references and index. ISBN 0-387-98756-8 (pbk. : acid-free paper) 1. Physics. I. Holton, Gerald James. II. Rutherford, F. James (Floyd James), 1924– III. Harvard Project Physics. Project physics course. IV. Title. V. Series. QC23.2 .C37 2002 530—dc21 2002020937 ISBN 0-387-98756-8 Printed on acid-free paper. © 2002 Springer-Verlag New York, Inc. All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed in the United States of America. 9 8 7 6 5 4 3 2 1 SPIN 15110102 Springer-Verlag New York Berlin Heidelberg A member of BertelsmannSpringer Science(cid:2)Business Media GmbH 3637_CassidyTX_00fm 6/19/02 12:08 PM Page v To the students and instructors whose advice, while using the draft versions of the text and guides, helped to improve our work greatly; and to Joan Laws, whose quiet expertise all these years helped to bring the project to success. This page intentionally left blank 3637_CassidyTX_00fm 6/19/02 12:08 PM Page vii Science is an adventure of the whole human race to learn to live in and perhaps to love the universe in which they are. To be a part of it is to understand, to un- derstand oneself, to begin to feel that there is a capacity within man far beyond what he felt he had, of an infinite extension of human possibilities. . . . I propose that science be taught at whatever level, from the lowest to the high- est, in the humanistic way. It should be taught with a certain historical under- standing, with a certain philosophical understanding, with a social understanding and a human understanding in the sense of the biography, the nature of the peo- ple who made this construction, the triumphs, the trials, the tribulations. —I.I. Rabi, Nobel Laureate in Physics This page intentionally left blank 3637_CassidyTX_00fm 6/19/02 12:08 PM Page ix Preface Understanding Physics is a completely revised, updated, and expanded edi- tion of the Project Physics Course. It is an integrated introductory physics course, developed with funding from the Carnegie Corporation and the Sloan Foundation and with the close cooperation of Springer-Verlag New York. In approach and content, Understanding Physics follows the trail blazed by the earlier versions, but it includes more recent developments in physics and a stronger emphasis on the relationships among physics, technology, and society. We have sought especially to incorporate the salient lessons of recent physics education research and practical experience gained in the classroom. The Audience Understanding Physics is written primarily for undergraduate college stu- dents not intending (at least initially) to enter careers in science or engi- neering. These may include liberal-arts students, business majors, prelegal, and prospective architecture students. We have found that when the course is taken with laboratory work, it has been deemed suitable by medical schools for premedical students. An important group that this course is intended to serve are persons who plan to teach, or are already teaching, in K–12 classrooms. As has been widely discussed, there is a special need for improvement in the science education of current and future teachers as an important step toward achiev- ing greater scientific literacy in general. Many states have recently incor- porated the contextual approach used in Understanding Physicsinto state sci- ence education criteria. It is in part to meet the challenges of teacher education that this course was developed as a resource, along with the usual pedagogical training. Since college students in introductory science courses usually represent a wide spectrum of expertise in science and mathematics, this book assumes ix 3637_CassidyTX_00fm 6/19/02 12:08 PM Page x x PREFACE no prerequisites in science or mathematics beyond high-school algebra, geometry, and general science. In this text we have taken great care to de- rive all necessary equations very patiently, but whenever possible we have used narrative text instead of equations to convey the meanings of laws and concepts. Even if students have taken physics in high school, they often still lack proficiency in even the most basic concepts and techniques. One of the aims of this course is to enable all students to gain experience and confidence with physical-science concepts and quantitative methods, and with an understanding of the nature of science itself. Of course, for classes in which the students are sufficiently prepared, instructors may decide to place more emphasis on quantitative or other aspects of physics as appro- priate. The course is designed with such flexibility in mind. The Approach A unique feature of this text, like its predecessor, is that it places the fun- damental concepts of physics within the broader humanistic and historical contexts in which they arose, but without handicapping students in tests that compare their performance with students who have taken a less broadly conceived, conventional physics course. Research has shown that students exposed to our approach gain a much deeper understanding of both the content and the processes of scientific research, as well as an appreciation not only of what we know, but also of how and why we think we know it. This approach has been endorsed by several national organizations, in- cluding the National Science Foundation, the Research Council of the National Academy of Sciences, and Project 2061 of the American Associ- ation for the Advancement of Science. The National Research Council stated in its National Science Education Standards:* In learning science, students need to understand that science re- flects its history and is an ongoing, changing enterprise. The stan- dards for the history and nature of science recommend the use of history in school science programs to clarify different aspects of sci- entific inquiry, the human aspects of science, and the role that sci- ence has played in the development of various cultures. Thus, Understanding Physics operates on two levels, providing both the fundamental concepts of physics and the humanistic and intellectual con- texts in which the concepts developed. In addition to the necessary con- cepts and equations, intentionally developed patiently, and using easy-to- visualize examples, it aims to convey a real sense of the nature of scientific *Washington, DC: National Academy Press, 1996; p. 107.