Klaus Lüders Robert O. Pohl Editors Pohl’s Introduction to Physics Volume 2: Electrodynamics and Optics With videos: Demonstrations and biography of Robert W.Pohl Pohl’s Introduction to Physics Klaus Lüders Robert Otto Pohl Editors Pohl’s Introduction to Physics Volume 2: Electrodynamics and Optics Editors Klaus Lüders Robert Otto Pohl Fachbereich Physik Department of Physics Freie Universität Berlin Cornell University Berlin, Germany Ithaca, NY, USA Translated by Prof. William D. Brewer, PhD, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany Additional material to this book can be downloaded from http://extras.springer.com. ISBN 978-3-319-50267-0 ISBN 978-3-319-50269-4 (eBook) https://doi.org/10.1007/978-3-319-50269-4 Library of Congress Control Number: 2017944730 © Springer International Publishing AG 2018 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, repro- duction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a war- ranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Preface to the 24th German Edition (2018) and the 2nd English Edition (2018) Accompanying Volume 1, this second volume of “Pohl” will be published in an up-to-date format, with a modern system of numbering of the chapters, equations and figures and with exercises at the end of each chapter. Once again, we have taken the opportunity to carry out a critical reading of the whole text. Along with numerous clarifications and new formulations, we have revised many figures and comments to conform with modern notation and symbols, in order to make reviewing the material and reference to other literature as straightforward as possible. As in Volume 1, we have carried out major revisions to the accompanying videos. In the e-book format, they will be readily accessible and can be opened directly by clicking on the links provided. This is true also of supplementary references from the Internet, and of the historical documentary “Simplicity is the Mark of Truth – the Life and Work of Robert Wichard Pohl” by the science journalist Ekkehard Sieker (see the Preface to the 22nd edition, sidenote). He has dealt extensively with the biography of Robert Wichard Pohl in Göttingen. Once again, it is our pleasure and duty to expressly thank the Erstes Physikalisches Institut at the Georg-August-Universität Göttingen and the Fachbereich Physik at the Freie Universität Berlin for generous support. Special thanks go to Prof. K. Samwer, Prof. G. Beuermann, Mr. J. Feist and Mr. C. Mahn from Göttingen, as well as most especially Dr. J. Kirstein from the Freie Universität Berlin, without whose help the preparation of the videos for this new edition would not have been possible. The first English edition of Pohl’s “Physical Principles of Electricity and Magnetism” appeared in 1930 (translated, as was his “Physical Principles of Mechanics and Acoustics” two years later, by Winifred M. Deans). It was published by Blackie & Son, Ltd., London and Glasgow. The translation was based on the second edition of Pohl’s “Einführung in die Physik, Elektrizitätslehre” (Julius Springer, 1929). The present new, second English edition is based on the 24th edition of “Pohls Einführung in die Physik”,Vol.2(Elektrizitätslehre und Optik, Springer Spektrum, Berlin Heidelberg 2018). Again, we gratefully acknowledge the help of Professor W.D. Brewer from the Fachbereich Physik of the Freie Universität Berlin, not only for carrying out the translation of the text with great quality and speed, but also, and this is probably even more important, for his help with the identification and clarification of unclear parts in the text and in our comments. The English-language readers will appreciate the numerous links he added for further information. We owe thanks also to E. Sieker for his translation and production of the English version of his video biography of R.W. Pohl, which is included in the links for this edition. We also wish to thank Dr. T. Schneider and the Springer-Verlag for making this edition possible, and for their generous help in carrying out its preparation and production. Berlin, Göttingen, Ithaca, March 2017 K. Lüders R.O. Pohl v From the Preface to the 23rd German Edition (2009) After the publication of Vol. 1 of R.W. POHL’s Introduction to Physics, covering the topics of Mechanics, Acoustics and Thermodynamics in a new, revised edition in 2008, we now follow it with this Vol. 2, dealing with Electromagnetism and Optics, likewise as a newly-revised edition. We have again taken the opportunity to add supplemental information where it seemed appropriate to us. In addition to new or revised comments and a number of clarifications in the text, the novel features include in particular a series of videos showing demonstration experiments as well as a collection of exercises for the readers. The chapter on Ferromagnetism from earlier editions was againincludedinthesectiononElectromagnetism. The additional videos for this edition were recorded under our own direction in the new physics lecture hall at the University of Göttingen, or else in cooperation with the Physics Didactics Group at the Free University in Berlin. The main part of the exercises on electromagnetism comes from the original English-language edition of 1930; however, we have again added new exercises to both the Electromagnetism and Optics sections. They deal in particular with questions which arise in the text, the figures, or the videos, and so provide additional information and an aid to understanding the concepts introduced; they are thus intended to make it easier for the reader to review and digest the material in the book. Berlin and Göttingen, June 2009 K. Lüders R.O. Pohl vii From the Preface to the 22nd German Edition ROBERT WICHARD POHL completed his three-volume “Introduction to Physics” in 1940 with the publication of the first edition of his “Optics”. After we had edited the new, revised first volume covering the fields of Mechanics, Acoustics and Thermodynamics in 2004, we decided to combine the chapters on the fundamentals of Electromagnetism and Optics into a second volume. As with the first volume, we wanted to make an appropriate selection of the material from the many previous editions. The present Vol. 2 is based on the 20th edition of the “Elektrizitätslehre” and the 12th edition of “Optik und Atomphysik”, both of which appeared in 1967. For this volume, as for Vol. 1, the IWF Wissen und Medien (Institute for Scientific Films) in Göttingen prepared short videos showing original demonstration experiments. They are made available with the book as a DVD. In addition, the DVD contains the historical documentary film1 “Simplicity is the Mark of Truth” (Original title: “Einfachheit ist das Zeichen des Wahren”, Pohl’s scientific motto; see the Comment), which was planned, researched and, together with the Düsseldorf production studio ‘Kiosque’, filmed by the scientific journalist Ekkehard Sieker. The film offers a detailed view of the life and work of Robert Wichard Pohl in Göttingen. It describes how R.W. Pohl, together with his famous colleagues Max Born and James Franck, made essential contributions to research and the teaching of physics in Germany in the 1920’s. The Physics Institutes of the University of Göttingen in those days became one of the internationally most important centers of physics. Max Born engaged early on in research into Einstein’s theory of relativity and made important contributions to the theoretical foundation of modern quantum theory. James Franck’s research interests likewise lay in the field of quantum mechanics, in particular in the areas of atomic and molecular physics. R.W. Pohl was a pioneer of solid-state physics, and through his research and as a brilliant teacher, he influenced generations of physicists from all over the world. The excellent standing of physics in Göttingen was brought to an abrupt end by the political takeover of the National Socialist (Nazi) Party at the end of January, 1933. Max Born and James Franck were forced to emigrate from Germany; R.W. Pohl remained as the sole physics professor in Göttingen. He was not a publicly political person – he was a scientist, whose area of commitment was in his Institute. 1 Video: “Simplicity is the Mark of Truth” – the Life and Work of Robert Wichard Pohl – http://tiny.cc/xucxny The title of this film is the translation of Pohl’s scientific motto, “Simplex sigillum veri”, under which he held his famous lectures over several decades. It was written on the front wall of the physics lecture hall in Göttingen, and was occasionally mistranslated by jokesters as “Sealing wax is the only truth”.