G. S. Landsberg as an Author and Editor of Physics Textbooks

V. A. Fabrikant

Only the connection of ideas with facts and observations, with the direction of thought, in my opinion, can operate in the proper direction; otherwise reality slips away, and fiction easily takes its place—something that has often happened, and something I wished with all my might to avoid in my exposition. More than anything, I wish to arouse curiosity.

D. I. Mendeleev
Preface to The Principles of Chemistry

In the many-sided activity of G. S. Landsberg, work on textbooks occupied a large and important place. The fruits of this work were the Elementary Textbook of Physics and Optics. Although these books are addressed to entirely different readers, both reveal the general characteristic features of G. S. Landsberg as a teacher. In writing and editing textbooks, G. S. Landsberg made broad use both of his enormous teaching experience and of the remarkable pedagogical ideas of L. I. Mandelstam.

The difficulties of creating textbooks in physics are well known. Especially difficult demands are placed on a textbook by the need not only to communicate a certain sum of factual knowledge, but also to cultivate in the student a correct worldview. Here the issue is not declarations, to which, unfortunately, many textbooks still resort, but the methodological education of a worldview through the analysis of concrete physical material. M. Laue, in his autobiography, cites, paradoxical as it may seem, a very correct winged phrase: “Education is what remains when everything learned has already been forgotten.”

For good Soviet textbooks, narrow utilitarianism and the desire to sidestep difficult questions connected with analyzing the content of basic physical concepts are entirely inadmissible. For learning, of course, textbooks that glide along the surface and do not penetrate into the essence of the matter are easier, but this ease is bought at a high price. In general, the tendency to make the student’s work with a textbook as easy as possible is a very dangerous tendency. It is easy to cultivate that “lazy credulity” of mind of which Maxwell once spoke in his introductory lecture to a course in physics, and to kill the curiosity about which Mendeleev wrote. The student trustingly follows the author past difficult places, and a fiction of understanding arises, based essentially on a peculiar “deception.”

We have dwelt on the problem of ease and difficulty because the books created by G. S. Landsberg are difficult books. But it seems to us that this is a justified difficulty, connected with the desire to give the student a clear conception of the physical essence of the questions under discussion, and not to “deceive” the student by carefully leading him away from real difficulties. A simplified exposition often cultivates formalism in students and an inability practically to apply the knowledge obtained.

Both books by G. S. Landsberg, in all their content and structure, are directed against formalism and dogmatism in the study of physics.

A concrete analysis of the content of these books only confirms what has been said.

The three volumes of the first edition of the Elementary Textbook of Physics appeared in 1948–1952. In 1956 the first volume appeared, and in 1957 the remaining two volumes of the second revised edition appeared. During this time the book gained general recognition and has already exerted a significant influence on the quality of physics teaching in secondary school.

The book is widely used by both teachers and students of secondary school.

In the preface to the first edition, the goals set before themselves by the group of authors headed by G. S. Landsberg are formulated.

This foreword, written by G. S. Landsberg, clearly sets forth his point of view on the tasks of teaching physics in secondary school and is of independent interest.

Here are several excerpts from this foreword.

“Among teachers in higher education there has arisen the sad conviction that the knowledge of physics with which pupils come from secondary school is at a completely unsatisfactory level. We are embarrassed not so much by a lack of facts and theoretical ideas available to the pupils as by the absence of a clear and correct judgment about their relationship. Pupils are often poorly oriented as to what is to be taken as the basis as a definition, what is the result of experience, and what should be regarded as a theoretical generalization of these experimental data.”

“Of course, in terms of the volume of material taught, the depth of exposition, and the systematic use of a more or less complex mathematical apparatus, teaching in higher education differs substantially from teaching at lower levels.

“However, even at these levels it is precisely physical science that must be taught (or an ‘introduction to it’), and not a complex of facts and knowledge.”

“A clear understanding of this experimental character of physical laws is of extremely great importance: it makes physics a science of nature rather than a system of speculative constructions; on the other hand, it instills the idea of the limits of applicability of established physical laws, of theories based on them, and opens prospects for the further development of science.

“No less important a role in the first steps of study is played by a correct conception of the schematization of the phenomena being studied, its meaning and value.”

“Teaching in secondary school, like any other teaching, cannot, of course, be exhaustive. But it must be structured in such a way that in the future the pupil can and should continue learning, yet would never be forced to relearn.”

“It was precisely these considerations, and not a desire to substantially alter the factual material, that played the decisive role. Therefore, in the present book rather much space is often allotted to those ‘simple’ questions which are usually presented in a few lines.”

The foreword to the second edition of the Elementary Textbook emphasizes the invariability of the book’s basic methodological principles, as tested by practice.

A very complex matter is taking account of the needs of polytechnical education in a physics textbook. A physics textbook, of course, should not replace textbooks in technical disciplines, but it must give a clear conception of the physical foundations of the most important branches of modern technology. It must be said that the Elementary Textbook satisfies this requirement to a considerable extent.

The first volume was written by S. E. Khaikin, M. A. Isakovich (Mechanics), M. A. Leontovich and L. I. Sakharev (Heat, Molecular Physics).

In mechanics, very much space is devoted to the analysis of such basic concepts as force, mass, and work. Everywhere a detailed picture is given of the origin of forces connected with deformations of bodies, which lends physical concreteness to the treatment of all questions of dynamics (especially in curvilinear motion).

The physical content of Newton’s laws is set forth clearly and vividly. The selection of examples in mechanics is very successful.

On the whole, mechanics is indeed presented as a branch of physics, without the usual formalism, and not only provides a store of useful information but, most importantly, introduces the student into the circle of the most fundamental physical ideas. The adopted system of presentation makes it possible to avoid the “relearning” required in higher school.

The mechanics of liquids and gases is presented very freshly and interestingly. Despite the elementary level of presentation, these chapters contain information on the results of modern aero- and hydrodynamic research.

The arrangement of the second part of the first volume has undergone rather substantial changes in the second edition. In the first edition the authors strictly observed the principle: first experimental data, and then theoretical interpretation. In the new edition the foundations of molecular theory are placed before the description of the properties of gases. This change seems methodologically correct to us. After all, Chapter XI, “Molecular Theory,” gives only a purely qualitative picture of molecular motions and interactions. Yet the presence of this picture makes it possible in the subsequent chapters to present experimental results and their theoretical interpretation in a unified manner.

All the material of the second part gives a clear and sufficiently complete conception of the basic thermal properties of bodies and of the molecular origin of their thermal and mechanical characteristics.

This material takes proper account of the needs of polytechnical education.

The second volume is devoted to electricity and magnetism.

The authors of the second volume are S. G. Kalashnikov and L. A. Tumerman. The final section is a relatively revised edition of the second edition.

A special chapter on semiconductors has been added; in connection with polytechnic education, the chapters setting forth the physical foundations of electrical engineering have been greatly expanded and reworked.

In presenting all the material of the volume, electronic concepts are widely used, which should be recognized as entirely correct. Likewise, in heat, a sharp division into pure phenomenology and into a microscopic picture of phenomena would be excessive pedantry. At the same time, the role of experiment is by no means diminished.

It seems to us especially important that the analysis of such important and difficult concepts as electromotive force and current velocity has been deepened. After all, the modernity of an exposition of the theory of electricity is determined to such an extent by including new, more profound treatment of the basic concepts.

On the whole, the volume presents a quite modern exposition of the theory of electricity and magnetism, with special attention devoted to the analysis of the basic physical concepts.

The third volume is devoted to oscillations, optics, and the structure of the atom. The authors of the third volume are F. S. Barshchanskii, S. M. Rytov, M. M. Sushchinskii, F. L. Shapiro, and I. A. Yakovlev.

It must be said that in secondary school all the material of the third volume is covered at a very rapid pace, literally at a gallop. Students’ knowledge of optics is of a very formal character. Even the simplest constructions of geometrical optics cause difficulty.

The third volume naturally begins with the mechanics of oscillations, treated very thoroughly and clearly.

Sound and electromagnetic oscillations and waves are set forth in great detail. There are even such subtleties as the phenomenon of parametric resonance. Photometry and geometrical optics are also expounded with unusual thoroughness. Optical devices are now widely used in the most diverse fields of science, technology, and culture, so that a clear understanding of the principles of their operation is necessary literally for everyone. The corresponding sections of the book provide every opportunity for this. The interference of light is presented comparatively briefly, which is justified by the presence of the previously placed article on the interference of mechanical waves.

Questions of the diffraction and polarization of light are also set forth briefly but clearly. Despite the difficulty, the inclusion of the question of resolving power should be acknowledged as correct. As in the other sections, much attention is given to the basic concepts.

In the chapter on the dispersion of light, quite rightly, much space is devoted to the analysis of questions connected with the origin of the colors of bodies. These questions are of great practical importance; everyone encounters them in everyday life, and at the same time few people have a clear idea of the causes determining the color of one body or another.

The attention given to spectra, spectral analysis, and the action of light is likewise justified.

The last part of the textbook—atomic physics—naturally presented great difficulties in writing. These difficulties have been successfully overcome, and the section indicated combines freshness of material with accessibility in the exposition of the basic questions. Despite the entirely justified predominance of descriptive material, the basic ideas of modern physics are also given in this section in the proper measure.

On the whole, the section “Atomic Physics” meets the requirements of an elementary textbook, not of a popular brochure, although it contains much material that is clearly nonessential.

The book concludes with a brief conclusion of a philosophical character, devoted to the struggle between materialism and idealism in contemporary physics. Such a conclusion seems to us quite appropriate, unlike those philosophical “introductions” which sometimes precede, rather than conclude, the exposition of concrete physical material. Such introductions do not reach the student, for they operate with concepts and facts still unknown to him.

Summing up the entire content of the textbook, it is necessary to note that in every section one feels the firm and skillful hand of the editor. The manner of exposition of individual sections changes in accordance with the character of their content, and not in connection with accidental peculiarities of the style of one author or another. The book does not have the motley quality characteristic of books written by large authorial collectives.

At the same time, the book skillfully makes use of all the advantages of a large authorial collective.

As a result, the textbook has become a handbook for teachers. In this book they draw not only new facts, not only a correct understanding of the basic physical concepts, but, most importantly, fresh methodological ideas. In using this

...books, teaching cannot be conducted in the old dogmatic style, which reduces to zero the entire educational significance of the physics course. The book was undoubtedly one of the incentives for raising the level of physics teaching in secondary school. According to the testimony of examiners at entrance examinations to higher educational institutions, pupils who have used the “Elementary Textbook” stand out sharply.

All this is due to the editorship of G. S. Landsberg, who devoted an enormous amount of time and labor to the creation of the book.

Let us turn to an examination of the university course Optics, which has already gone through three editions. Shortly before his death, G. S. Landsberg carefully prepared the fourth edition, which is soon to appear in print.

It must be said that optics, generally speaking, has been fortunate as regards the number of good textbooks. It is enough to recall the books of Planck, Drude, Schuster, Born, and Schäfer. But all these books are textbooks of theoretical optics. At the other extreme is the brilliant and distinctive book by Wood, in which, as is well known, not everything is quite satisfactory, even in the Russian translation carefully edited by D. S. Rozhdestvenskii.

If, however, one speaks of optics as a section of a general physics course, then here there were undoubtedly successful, but already outdated books: these are, first of all, the well-known synopsis by A. A. Eikhenvald and D. A. Rozhanskii’s Optics in the course edited by A. F. Ioffe. Standing apart is Pohl’s book, which is an indispensable aid for the instructor, but is too idiosyncratic for the average student.

We have deliberately recalled the richness of the educational literature on optics in order to emphasize the background against which G. S. Landsberg’s Optics appeared.

G. S. Landsberg’s book has taken its own, and an honorable, place among the books mentioned. It is undoubtedly the best and most modern of the books presenting “Optics” at the level of a general university physics course. In it that “connection of ideas with facts” of which Mendeleev wrote is realized.

The book grew out of lectures delivered by G. S. Landsberg at Moscow University. For a textbook, such a path of origin is the most rational, for the author could take full account of the reaction of the student audience. In the preface to the first edition G. S. notes the strong influence of L. I. Mandelstam on the course he delivered. Each subsequent edition was revised by G. S. Landsberg with his characteristic thoroughness. Our brief review will be devoted to the third edition.

The book includes all the basic factual material of optics as a physical discipline, but this circumstance makes it a genuinely modern textbook of optics. The decisive mark is the manner of exposition of the fundamental theoretical problems and the profound physical analysis of the basic concepts.

The book educates the student not only in the ability to think physically, but also in love and interest for the precise physical experiment. The student feels that the book was written by a scientist who loves his field of science, and this has no small educational significance, which should not be forgotten.

A university general course of physics poses considerable difficulties for the teacher. It is necessary to combine great depth of physical analysis with strict limitations in the use of the mathematical apparatus, and to assign much room to the description of experiments without falling into a purely descriptive style. In the book the proportions necessary for a general physics course are observed. True, many derivations which, in essence, go beyond the limits of the general course are placed in the form of exercises at the end of the book.

The book begins with an introduction which, despite its brevity, gives a very interesting and fresh historical outline of the development of optics. In this outline, in particular, an entirely just “rehabilitation” of Newton’s optical ideas is carried out, and the role of Huygens in the development of optics is clarified.

The first section—“Interference of Light”—contains a very deep analysis of the conditions for observing interference (the role of the size of the source, aperture, polarization, localization of fringes). Characteristic is the presence of a special paragraph devoted to interference paradoxes. Here the influence of L. I. Mandelstam is clearly evident; he rightly considered the analysis of paradoxes a very good method for studying physical problems.

The second section—“Diffraction of Light”—begins with a detailed formulation of the Huygens–Fresnel principle, to which the author returns in § 40.

Here, in accordance with G. S. Landsberg’s general methodological principles, much attention is given to discussion of the physical meaning of the Huygens–Fresnel principle. In contrast to the usual exposition, emphasis is placed on the limits of applicability of this principle. The question of the limits of applicability of one or another physical relation has enormous educational significance. Discussion of this question teaches the student rigor of thought and gives him the opportunity to feel the living spirit of science, which ceases to look like something completely frozen in its final forms.

The analysis of particular cases of diffraction is carried out in a clear and simple form, and such questions as the role of a spectral apparatus in the analysis of a light pulse are examined qualitatively.

Geometrical optics is placed after wave optics, which makes it possible to speak of it as a limiting case of wave optics.

Geometrical optics includes an analysis of resolving power according to Rayleigh and elements of microscope theory by Abbe, with substantial refinements by L. I. Mandelstam. Here, too, a vivid and clear exposition is given of the very difficult question of the phase-contrast method.

The section “Polarization of Light” includes the very important § 101, devoted to the internal structure of natural light and discussing S. I. Vavilov’s instructive experiment. This paragraph is very useful for understanding the fundamental properties of natural light.

The section “Velocity of Light” is very successful. It not only examines all the basic methods for determining the velocity of light, but also gives a brief exposition of the foundations of the optics of moving media. It seems to us very correct and modern that here a detailed analysis is also given of the concept of group velocity, which is usually postponed until the theory of dispersion. After all, the very fact of the dependence of phase velocity on frequency is not difficult to grasp.

Rømer’s method is presented close to the original, which is methodologically more successful than the sometimes used argument involving the velocity of the Earth’s motion. The difficult questions of the optics of moving media are set forth very clearly.

In the section “Passage of Light through the Boundary of Two Media,” a detailed discussion is given of the physical consequences of the Fresnel formulas and of the indicated limits of their applicability. Of great importance is the presence of a qualitative microscopic picture of the propagation of a light wave in a medium.

In the section “Optics of Anisotropic Media,” the basic question of applying Huygens’ construction in anisotropic media is analyzed with unusual precision and clarity, and the phenomenon of anisotropy receives sufficient attention.

The ninth section, “Molecular Optics,” gives, in a semiquantitative form, a picture rich in physical content of the phenomena of dispersion, absorption, and scattering of light.

These questions were close to G. S. Landsberg’s field of scientific interests, which, naturally, had a very positive effect on their exposition. Particular attention is paid to the extremely important concept of an optically homogeneous medium. This is precisely one of those “simple” concepts that are usually not analyzed clearly enough. It is characteristic of G. S. Landsberg that, in the exposition of the entire section, the results of Soviet scientists are widely and appropriately used. At the end of the section the insufficiency of classical ideas for explaining all the phenomena of molecular optics is pointed out.

The next section—“Actions of Light”—already naturally belongs to the field of quantum optics.

The chapter on the photoelectric effect characterizes the main experiments in this field rather comprehensively. It is important that the wave properties of light in the photoelectric effect are emphasized (§ 171). This is of fundamental importance for the correct understanding of the duality of the properties of light. Usually one is limited only to indicating the role of the corpuscular properties of light in the photoelectric effect.

The mechanical actions of light (the Compton effect and light pressure) are considered comparatively briefly, but clearly. The fact that they are brought together appears methodologically correct, since the Compton effect may be regarded as the pressure of light on individual electrons.

The section “Thermal Radiation” is constructed very harmoniously and contains everything necessary, beginning with a profound analysis of the features of this type of radiation and ending with the basic problems in the field of pyrometry and the technology of light sources.

Under the heading “Luminescence,” G. S. Landsberg brought together a large circle of problems connected with the occurrence of radiation in gaseous, liquid, and solid bodies. Here, too, the Vavilov–Cherenkov effect is included, as a vivid illustration of the application of S. I. Vavilov’s well-known criterion for establishing the nature of radiation.

It should be emphasized that, along with a deep analysis of the basic physical concepts, in all sections sufficient space is devoted not only to experiment, but also to the physical foundations of the practical applications of optics.

Here, as it were, that combination of “pure” physics with its practical applications is reflected, which occupied a considerable place in the activity of G. S. Landsberg himself. The exercises play a very distinctive role in the book. In them the reader is given the opportunity, with the author’s very tactful assistance, to derive independently a number of such basic relations as the Fresnel formulas, Planck’s formula, etc. This,

of course, greatly stimulates the reader’s work with the book. The same purpose is served by the numerous well-designed problems included in the exercises.

The book concludes with a section of a general methodological character, in which light is considered as one of the forms of matter. We have already discussed above the appropriateness and usefulness of such a conclusion in connection with an elementary textbook. In a textbook for higher education, such a conclusion is all the more necessary.

The analysis we have carried out shows that G. S. Landsberg’s book fully deserves the high esteem in which it has been held by broad circles of readers. It is, of course, not only a textbook for university students. It is used by everyone who wishes to gain insight into the essential physical content of contemporary optics.

Our analysis shows how consistently G. S. Landsberg pursued his pedagogical ideas in the textbooks he created. Thanks to this, the textbooks bearing G. S. Landsberg’s name will for many years continue to do their useful work, helping young people study genuine physics as a living science, and not as a bare and rigid scheme.