CL. SCHAEFER, Theoretical Physics, Vol. III, Part 2, Optics, translated from the German by G. M. Katto, N. N. Malov, and E. L. Starokadamsky, edited by Prof. K. F. Teodorchik, GONTI, 1938, 523 pp. with figures and plates.

The course of theoretical physics by Cl. Schaefer, the well-known researcher and teacher, is familiar to the Soviet reader. The merits of this course were already duly appreciated after the appearance of its first volumes. Therefore the completion of the publication of Schaefer’s course of theoretical physics in Russian in the classical part of the course can only be welcomed in every way. Pedagogical merits of the course—clarity and precision of exposition, careful mathematical appendices, explanation of the physical meaning of every detail in the calculation, selection of material, etc.—make this course an indispensable aid for students of physics-and-mathematics faculties of pedagogical institutes and universities. The merits of the previously issued volumes of Schaefer’s course of theoretical physics are also characteristic of the book under review.

The contents of Optics are as follows. In the first three chapters—Optics of transparent media, Optics of nontransparent media, Optics of crystals—the laws of the passage of plane electromagnetic waves through these media are considered. The next two chapters are devoted to the phenomena of interference and diffraction. These, in fact, conclude the exposition of Maxwell’s electrodynamics (in its optical part, set forth in the first part of the third volume). The following chapter is entitled “Electron Theory and Dispersion.” Here the general foundations of Lorentz’s theory of electrons are presented, and some of its applications, chiefly to the phenomena of dispersion, are also considered. The last two chapters—Theory of Radiation and Theory of Relativity—stand somewhat apart and are not organically connected with the preceding chapters. It should be regretted that geometrical optics and molecular optics are represented only slightly in the book. From the section on geometrical optics, essentially only Fermat’s principle and the eikonal equation are considered; molecular optics is in fact absent. Questions of radiation are considered in the penultimate chapter only from the thermodynamic point of view; thus the description of the radiation of a damped oscillator also found no place in Schaefer’s course of theoretical physics.

The paragraphs devoted to the total internal reflection and dispersion are presented in an original way and therefore are of interest not only to the teacher and the student. In the course there is also a very detailed calculation, carried out by Schaefer, of the diffraction of electromagnetic waves by a cylinder. In the rest, Schaefer, as usual, follows the classical models in his exposition.

Following his rule, Schaefer frees the reader from the necessity of performing calculations in vector symbolism. In calculations with waves he does not use the wave vector \(\vec K = \dfrac{\lambda\pi}{\lambda}\,\vec s\), which, as it seems to us, leads to an unnecessary cumbersomeness in most of the formulas. This applies especially to all calculations connected with the investigation of the phenomena of reflection and refraction.

As to the substance of the exposition, the following comments should be made. It is hardly advisable to set forth proof of the fact of the rectilinear propagation of light according to Fresnel if Kirchhoff’s formula is subsequently derived. From the latter formula the same conclusion follows more simply and elegantly. The exposition of relativistic mechanics is unfortunate (in the po-

…following chapter): the equations of relativistic mechanics do not need derivation, just as Newton’s equations do not. The logical transition from Newton’s equations to relativistic ones could have been shown much more simply.

An unquestionable merit of the book is the fact that very great attention is devoted in it to questions of the coherence of light. The question of the coherence of light is considered in several chapters and from various points of view. This is all the more successful because in other monographs on optics these questions, so rich in physical content, are usually touched upon only in passing.

It seems that Schaefer’s course in physics brings to an end the tradition that has existed up to now, consisting in the separate exposition of the theories of Maxwell and Lorentz. All electrodynamic phenomena are fitted into a sufficiently coherent theoretical scheme, and there is, it seems to us, no need to conduct this exposition in the end of the book, returning after the exposition of Maxwell’s theory to the origins of the course and introducing the corresponding additions that take into account the discrete structure of the medium. The necessity for a new course of theoretical physics, presenting the material from somewhat different positions, more economically and logically coherently, has undoubtedly matured. One would like to think that such a course will be written by Soviet physicists. This, of course, does not hinder us from rejoicing at the completion of the publication of the solid and very valuable Course of Theoretical Physics by Schaefer for our students.

The translation of the book has been done well. The production—printing and plates—is satisfactory.

A. Kitaigorodsky, Moscow