MATTER AND LIGHT The New Physics BY LOUIS DE BROGLIE Memhre de VInstitut Nobel Pri e Award 192 Professeur la Facultl des Sciences de Paris TRANSLATED BY W. H. JOHNSTON, B. A. New York W W NORTON CO - INC Publishers entitled Jtfattere e . Lur ilre was first published in 1937 T, FIRST EDITION PUBLISHED IN ENGLISH IN 1939 BY W - W NORTON COMPANY INC 70, FIFTH AVENUE, NEW YORK All rights reserved BINDERY JAM 2 9 1945 990361 PRINTED IN GREAT BRITAIN TRANSLATORS NOTE THE Author has in certain places modified the original French text for the English translation, for the sake of greater cohesion, and has also revised some passages, in order to bring them into accord with the results of later research. Occasional Translators Notes are shown in square brackets. The chapter on The Undulatory Aspects of the Electron has the special historical interest of having been delivered as a Lecture on the occasion of the Authors receipt of the Nobel Award, while that on Wave Mechanics and its Interpretations was given as an Address at the Glasgow meeting of the British Association in 1928. I am indebted to Dr. J. E. Turner, of the University of Liver pool, for assistance with the translation and the proofs, and to Dr. C. Strachan, of the same University, I am indebted for valuable assistance in dealing with the equations and the more technical passages, as well as for reading the proofs. W. H. J. PREFACE THE amiable insistence of my friend Andr George has induced me to collect in the present Volume a number of Studies on con temporary Physics written from both the general and the more metaphysical point of view. Each of these Studies forms an inde pendent whole, and can be read by itself. A slight degree ofrepeti tion which the reader is asked to overlook has been the inevi table result for on more than one occasion I have been compelled to duplicate a summary of the great fundamental stages of con temporary Physics, such as the classification of simple substances, the investigation of the photo-electric effect and the origin of the Theory of Light Quanta and of Wave Mechanics the subjects are somewhat technical, and I cannot well assume that they are common knowledge. But though the same subject is outlined in several of these Studies, I have tried to take up a different point of view in each, and have endeavoured to throw light on different aspects of the essential problems of Quantum Physics in order to facilitate a grasp of their importance. On comparing the different chapters the reader will observe that, while overlapping, they also complement one another and he will feel the fascination and greatness inherent in the vast structure of modern Physics. And while admiring the vast number and the extreme delicacy of experimental facts which laboratory physicists have succeeded in revealing, and the strange and brilliant concepts devised by theorists to explain them, he will appreciate to what a degree the methods and ideas of physicists have grown in subtlety during recent years, and how great has been the progress from the somewhat ingenuous Realism and the over-simplified Mechanics of earlier thinkers. The more deeply we descend into the minutest structures of Matter, the more clearly we see that the concepts evolved by the mind in the course of everyday experience especially those of Time and Space must fail us in an endeavour to describe the new worlds which we are entering. Onefeels tempted to say that the outlines of our concepts must undergo a io MATTER AND LIGHT progressive blurring, in order that they may retain some semblance of relevance to the realities of the subatomic scales. Time and Space, in other words, are too loose a dress for the elementary entities individuality becomes attenuated in the mysterious pro cesses of interaction, and even Determinism, the darling of an older generation of physicists, is forced to yield...

AN INTRODUCTION TO THE STUDY OF WAVE MECHANICS by LOUIS DE BROGLIE. Originally published in 1930. Contents include: INTRODUCTION 1 CHAPTER I HE OLD SYSTEMS OF MECHANICS OP A PARTICLE 11 CHAPTER II J HB THEORY OF JACOBI 26 CHAPTER III THE CONCEPTIONS UNDERLYING WAVE MECHANICS 39 CHAPTER IV GENERAL REMARKS ON WAVE PROPAGATION 49 CHAPTER V THE EQUATIONS OF PROPAGATION OF THE WAVE ASSOCIATED WITH A PARTICLE 68 CHAPTER VI CLASSICAL MECHANICS AND WAVE MECHANICS 79, CHAPTER VII THE PRINCIPLE OF INTERFERENCE AND THE DIFFRACTION OF ELECTRONS BY CRYSTALS 88 CHAPTER VIII THE PRINCIPLE OF INTERFERENCE AND THE SCATTERING OF CHARGED PARTICLES BY A FIXED CENTRE 102 CHAPTER IX THE MOTION OF THB PROBABILITY WAVE IN THE NEW MECHANICS . .111 CHAPTER X THE WAVE MECHANICS OF LIGHT QUANTA, 12 CHAPTER XI THE THEORY OF BOHR AND HBWENBERG vi An Introduction to the Study of Wave Mechanics CHAPTER XII PAG THB POSSIBILITY OF MEASUREMENT AND HBISENBERGS RELATIONS ., 1 CHAPTER XIII THE PROPAGATION OF A TRAIN OF -WAVES IN THE ABSENCE OF A FIELD OF FORCE AND IN A UNIFORM FIELD 1 CHAPTER XIV WAVE MECHANICS OF SYSTEMS OF PARTICLES IVs CHAPTER XV THE INTERPRETATION OF THE WAVE ASSOCIATED WITH THE MOTION OF A SYSTEM 188 CHAPTER XVI THE OLD QUANTUM THEORY AND THE STABILITY OF PERIODIC MOTION . 199 CHAPTER XVII THE STABILITY OF QUANTISED MOTION FROM THE POINT OF VIEW OF WAVE MECHANICS .... 212 CHAPTER XVIII SOME EXAMPLES OF QUANTISATION 227 CHAPTER XIX THE MEANING OF THE -WAVES OF QUANTISED SYSTEMS .... 238 INDEX 247. AN INTRODUCTION TO THE STUDY OF WAVE MECHANICS. GENERAL INTRODUCTION: THE new wave mechanics has received during the past two years the firm support of experiment, thanks to the discovery of a strikingphenomenon completely unknown previously, viz. the diffraction of electrons by crystals. From one point of view it may be said that this discovery is the exact counterpart of the older discovery of the photo electric effect, since it shows that for matter as for light we have hitherto neglected one of the aspects of physical reality. The discovery of the photo-electric effect has taught us that the undulatory theory of light, firmly established by Fresnel and subsequently developed by Maxwell as the electro magnetic theory, although it contains a large body of truth, is, nevertheless, insufficient, and that it is necessary, in a certain sense, to turn again to the corpuscular conception of light proposed by Newton. Planck, in his famous theory of black body radiation, was led to assume that radiation of frequency v is always emitted and absorbed in equal and finite quantities, in quanta of magnitude hv, h being the constant with which the name of Planck will always be associated. In order to explain the photo-electric effect, Einstein had only to adopt the hypothesis, which is quite in conformity with the ideas of Planck, that light consists of corpuscles and that the energy of the cor puscles of light of frequency v is hv. When a light corpuscle in its passage through matter encounters an electron at rest, it can impart o it its energy hv and the electron thus set in 1 This introduction is the reproduction of a communication made by the author at the meeting of the British Association for the Advance ment of Science held in Glasgow in September, 1928, 1 2 An Introduction to the Study of Wave Mechanics motion will leave the matter with kinetic energy equal in amount to the differencebetween the energy hv, which it has received, and the work it has had to expend to get out of the matter. Now, this is precisely the experimental law of the photo-electric effect in the form which has been verified in succession for all the radiations from the ultra-violet region to X-and y-rays...

This classic work in the philosophy of physical science is an incisive and readable account of the scientific method. Pierre Duhem was one of the great figures in French science, a devoted teacher, and a distinguished scholar of the history and philosophy of science. This book represents his most mature thought on a wide range of topics.

AN INTRODUCTION TO THE STUDY OF WAVE MECHANICS BY LOUIS DE BROGLIE DOCTEUB 8-8CIENCES, PROFESSOR IN THE HENRI POISCAR INSTITUTE, PARIS TRANSLATED FROM THE FRENCH BY H. T. FLINT, D. Sc., PH. D. WITH FOURTEEN DIAGRAMS I METHUEN C0. LTD. 36 ESS-EX f EET W. C. First Published in 1930 CONTENTS PAGE PBNBBAL INTRODUCTION 1 CHAPTER I HE OLD SYSTEMS OF MECHANICS OP A PARTICLE 11 CHAPTER II J HB THEORY OF JACOBI 26 CHAPTER III THE CONCEPTIONS UNDERLYING WAVE MECHANICS 39 CHAPTER IV GENERAL REMARKS ON WAVE PROPAGATION 49 CHAPTER V THE EQUATIONS OF PROPAGATION OF THE WAVE ASSOCIATED WITH A PARTICLE 68 CHAPTER VI CLASSICAL MECHANICS AND WAVE MECHANICS 79, CHAPTER VII THE PRINCIPLE OF INTERFERENCE AND THE DIFFRACTION OF ELECTRONS BY CRYSTALS 88 CHAPTER VIII THE PRINCIPLE OF INTERFERENCE AND THE SCATTERING OF CHARGED PARTICLES BY A FIXED CENTRE 102 CHAPTER IX THE MOTION OF THB PROBABILITY WAVE IN THE NEW MECHANICS . .111 CHAPTER X THE WAVE MECHANICS OF LIGHT QUANTA, 12 CHAPTER XI THE THEORY OF BOHR AND HBWENBERG vi An Introduction to the Study of Wave Mechanics CHAPTER XII PAG THB POSSIBILITY OF MEASUREMENT AND HBISENBERGS RELATIONS ., 1 CHAPTER XIII THE PROPAGATION OF A TRAIN OF -WAVES IN THE ABSENCE OF A FIELD OF FORCE AND IN A UNIFORM FIELD 1 CHAPTER XIV WAVE MECHANICS OF SYSTEMS OF PARTICLES IVs CHAPTER XV THE INTERPRETATION OF THE WAVE ASSOCIATED WITH THE MOTION OF A SYSTEM 188 CHAPTER XVI THE OLD QUANTUM THEORY AND THE STABILITY OF PERIODIC MOTION . 199 CHAPTER XVII THE STABILITY OF QUANTISED MOTION FROM THE POINT OF VIEW OF WAVE MECHANICS .... 212 CHAPTER XVIII SOME EXAMPLES OF QUANTISATION 227 CHAPTER XIX THE MEANING OF THE -WAVES OF QUANTISED SYSTEMS .... 238 INDEX 247 AN INTRODUCTION TO THESTUDY OF WAVE MECHANICS GENERAL INTRODUCTION l THE new wave mechanics has received during the past two years the firm support of experiment, thanks to the discovery of a striking phenomenon completely unknown previously, viz. the diffraction of electrons by crystals. From one point of view it may be said that this discovery is the exact counterpart of the older discovery of the photo electric effect, since it shows that for matter as for light we have hitherto neglected one of the aspects of physical reality. The discovery of the photo-electric effect has taught us that the undulatory theory of light, firmly established by Fresnel and subsequently developed by Maxwell as the electro magnetic theory, although it contains a large body of truth, is, nevertheless, insufficient, and that it is necessary, in a certain sense, to turn again to the corpuscular conception of light proposed by Newton. Planck, in his famous theory of black body radiation, was led to assume that radiation of frequency v is always emitted and absorbed in equal and finite quantities, in quanta of magnitude hv, h being the constant with which the name of Planck will always be associated. In order to explain the photo-electric effect, Einstein had only to adopt the hypothesis, which is quite in conformity with the ideas of Planck, that light consists of corpuscles and that the energy of the cor puscles of light of frequency v is hv. When a light corpuscle in its passage through matter encounters an electron at rest, it can impart o it its energy hv and the electron thus set in 1 This introduction is the reproduction of a communication made by the author at the meeting of the British Association for the Advance ment ofScience held in Glasgow in September, 1928, 1 2 An Introduction to the Study of Wave Mechanics motion will leave the matter with kinetic energy equal in amount to the difference between the energy hv, which it has received, and the work it has had to expend to get out of the matter. Now, this is precisely the experimental law of the photo-electric effect in the form which has been verified in succession for all the radiations from the ultra-violet region to X-and y-rays...

MATTER AND LIGHT The New Physics BY LOUIS DE BROGLIE Memhre de VInstitut Nobel Pri e Award 192 Professeur la Facultl des Sciences de Paris TRANSLATED BY W. H. JOHNSTON, B. A. New York W W NORTON CO - INC Publishers entitled Jtfattere e . Lur ilre was first published in 1937 T, FIRST EDITION PUBLISHED IN ENGLISH IN 1939 BY W - W NORTON COMPANY INC 70, FIFTH AVENUE, NEW YORK All rights reserved BINDERY JAM 2 9 1945 990361 PRINTED IN GREAT BRITAIN TRANSLATORS NOTE THE Author has in certain places modified the original French text for the English translation, for the sake of greater cohesion, and has also revised some passages, in order to bring them into accord with the results of later research. Occasional Translators Notes are shown in square brackets. The chapter on The Undulatory Aspects of the Electron has the special historical interest of having been delivered as a Lecture on the occasion of the Authors receipt of the Nobel Award, while that on Wave Mechanics and its Interpretations was given as an Address at the Glasgow meeting of the British Association in 1928. I am indebted to Dr. J. E. Turner, of the University of Liver pool, for assistance with the translation and the proofs, and to Dr. C. Strachan, of the same University, I am indebted for valuable assistance in dealing with the equations and the more technical passages, as well as for reading the proofs. W. H. J. PREFACE THE amiable insistence of my friend Andr George has induced me to collect in the present Volume a number of Studies on con temporary Physics written from both the general and the more metaphysical point of view. Each of these Studies forms an inde pendent whole, and can be read by itself. A slight degree ofrepeti tion which the reader is asked to overlook has been the inevi table result for on more than one occasion I have been compelled to duplicate a summary of the great fundamental stages of con temporary Physics, such as the classification of simple substances, the investigation of the photo-electric effect and the origin of the Theory of Light Quanta and of Wave Mechanics the subjects are somewhat technical, and I cannot well assume that they are common knowledge. But though the same subject is outlined in several of these Studies, I have tried to take up a different point of view in each, and have endeavoured to throw light on different aspects of the essential problems of Quantum Physics in order to facilitate a grasp of their importance. On comparing the different chapters the reader will observe that, while overlapping, they also complement one another and he will feel the fascination and greatness inherent in the vast structure of modern Physics. And while admiring the vast number and the extreme delicacy of experimental facts which laboratory physicists have succeeded in revealing, and the strange and brilliant concepts devised by theorists to explain them, he will appreciate to what a degree the methods and ideas of physicists have grown in subtlety during recent years, and how great has been the progress from the somewhat ingenuous Realism and the over-simplified Mechanics of earlier thinkers. The more deeply we descend into the minutest structures of Matter, the more clearly we see that the concepts evolved by the mind in the course of everyday experience especially those of Time and Space must fail us in an endeavour to describe the new worlds which we are entering. Onefeels tempted to say that the outlines of our concepts must undergo a io MATTER AND LIGHT progressive blurring, in order that they may retain some semblance of relevance to the realities of the subatomic scales. Time and Space, in other words, are too loose a dress for the elementary entities individuality becomes attenuated in the mysterious pro cesses of interaction, and even Determinism, the darling of an older generation of physicists, is forced to yield...