BIBLIOGRAPHY

NEW TEXTBOOKS ON OPTICS

1. G. S. Monk, Light, Principles and Experiments, McGraw-Hill Book Co, New-York and London, 1937, Pp. XI + 477, $ 5.

2. F. A. Jenkins and H. E. White, Fundamentals of Physical Optics, McGraw-Hill Book Co, New-York and London, 1937, XIV + 453, $ 5.

The appearance of two new American textbooks on optics should be warmly welcomed. Optics belongs among the most difficult branches of physics to master, while until quite recently the choice of textbooks here was extremely limited. Edser’s excellent book has become very outdated, and, moreover, the author’s tendency to restrict himself only to the methods of elementary mathematics makes the mathematical conclusions of the author needlessly cumbersome. Among books of a somewhat higher level one may mention Bruhat’s manual,¹ but this book is very bulky (756 pages of small print), and using it as a textbook is therefore difficult; the smaller English book by Houstoun² (apparently the most widespread textbook in England) is provided with poor diagrams. Alongside these there are excellent manuals of a considerably higher level. Drude’s book is still in many respects a model; the more modern manual of theoretical optics by M. Born is distinguished by the elegance of its mathematical form of exposition, but for the average student it is difficult and, of course, overly lengthy. Finally, the classical book by Wood, acquaintance with which is indispensable for every physicist, in no way can be regarded as a textbook. It should also be noted here that the appearance of the last three books in Russian translation is a great credit to our publishers; however, it must also be pointed out that whereas the books by Drude and Wood have been translated and published in Russian with great care and affection, this cannot be said of the Russian edition of Born’s book—the translation is in places unsatisfactory, and the edition is extremely careless.³

From this brief survey it is clear that the appearance of two thoroughly modern textbooks of optics, well conceived pedagogically, is very timely.

1. Monk’s book encompasses both physical and geometrical optics. The first 8 chapters (100 pages) are devoted to the latter (together with photometry). The exposition of geometrical optics opens with the formulation—

¹ Bruhat, Cours d’Optique, Masson et Cie Editeurs, Paris 1931, Pp. IX + 756.

² R. A. Houstoun, A Treatise of Light, Longmanns Green and Co, 1925, Pp. XI + 486.

³ The Russian translation of Born’s book was issued by the State Scientific-Technical Publishing House of Ukraine, which has published a number of other good books on physics, but, unfortunately, as a rule in an unsatisfactory form. Attention should be drawn to this.

The main principles (the concept of the ray, Fermat’s principle, the principle of reversibility, Malus’s theorem). Further on, thin and thick lenses, optical systems, and diaphragms are considered. The defects of the optical image are examined in detail. The section ends with the theory of optical instruments and a discussion of the eye as an optical instrument.

The next 9 chapters (pp. 100–339) are devoted to physical optics. In Ch. IX—“The Nature of Light”—the general properties of wave motion are set forth, along with Huygens’ principle in its original elementary form, and methods for determining the speed of light. Of the latter, only the classical methods are considered (Fizeau, Foucault, Michelson); the application of the Kerr effect to measuring the speed of light is mentioned only in Ch. XVI. Optical phenomena among experiments of Fizeau and Michelson are not touched upon. Chs. X and XI are devoted to interference. Alongside the classical interference experiments, the Michelson, Fabry and Perot interferometers are considered in detail. It is very surprising that the author omits the question of equal-inclination and equal-thickness fringes. There is no chapter on diffraction, nor any account of the Fresnel interpretation of Huygens’ principle, but this question is considered very superficially and leaves the reader with considerable dissatisfaction. Further on, the principal cases of Fresnel diffraction (with the aid of the Cornu spiral) and Fraunhofer diffraction (a single slit, two slits, a grating) are explained. Questions related to the resolving power of optical instruments are systematically considered only in connection with the diffraction grating and, in addition, are mentioned incidentally in various places in the book. There are no special paragraphs devoted to the diffraction theory of the formation of the optical image (unless § 6 of Ch. VII in geometrical optics is counted, from which the student, probably, will not take anything away). The chapter on diffraction is illustrated with good photographs. In Ch. XIII polarization and double refraction are considered. Ch. XIV is devoted to spectra. Alongside the exposition of factual material, the foundations of the quantum theory of line spectra (according to Bohr) are also given here, and even the theory of band spectra. Owing to the brevity of the exposition, this chapter cannot be useful to the student. This may be understood, for example, from the following exposition of the important and difficult question of the width of spectral lines: “In quantum mechanics, the discrete energy levels postulated by Bohr’s theory are considered rather as positions (?) of maxima in the probability distribution of energy values (??)” (p. 268). Or further: “It follows that when an atom absorbing or emitting energy collides with another atom, the phase and amplitude of the radiation may change. This leads to a half-width equal to n, etc.” (p. 269). In Ch. XV—“Light and Material Media”—a very wide range of phenomena is briefly considered (dispersion, absorption, the Raman effect, fluorescence, the photoelectric effect). Since the book gives no even brief systematic exposition of the electromagnetic theory of light, paragraphs such as “The Electromagnetic Theory of Dispersion” or “Metallic Reflection” are left hanging in the air; § 15.8, “The Quantum Theory of Dispersion,” is completely incomprehensible and, in essence, meaningless. Equally unfortunate should be considered the author’s attempt to expound in Ch. XVI the quantum theory of the normal and anomalous Zeeman effect (the latter without any mention of the anomalous features of spin and the Landé factor). It would have been far better had the author explained only and clearly the classical theory of the normal effect, but for some reason he does not do this, and he sends the reader to Hauschtka’s textbook. Chapter XVII—“The Eye and Color Vision”—brings to an end the theoretical part of the book.

The last part of the book—the description of laboratory work in optics—is very interesting. Alongside the usual easy exercises, serious and interesting problems with interferometers, the study of elliptical polarization, metallic reflection, and others are described here. In the “Appendices” some theoretical questions (Fresnel integrals, more complex questions of geometrical optics) and experimental questions are considered.

(manufacture of metallic mirrors, standard sources for colorimetry, etc.). At the end of the book useful tables and solutions are given for about 100 computational problems placed in the text of the book (after each chapter).

Summing up, it may be said that Monk’s book, despite a number of rather substantial shortcomings, will undoubtedly be useful for the instructor. Especially valuable in it are the chapters devoted to geometrical optics and the final experimental part.

1. Jenkins and White’s book differs substantially from M. Vol’f’s book. First, this book is devoted to physical optics; second, the authors have sensibly limited their task to the consideration of the classical questions of physical optics. Quantum problems are touched upon only lightly, and this is entirely proper, since their clear exposition requires a special book. Third, what immediately attracts attention is the abundance of original, well-conceived, and excellently executed drawings and photographs.

The book begins with a consideration of the general properties of wave motion (Chs. I and II). The exposition of many questions here is nontrivial and gives the specialist reader great pleasure. Chapter II—“Superposition of Waves”—should be especially noted. The authors at once introduce the vector method of adding many amplitudes, which is widely used throughout the book. In § 2.4, by means of a graphical method, the question of the superposition of many waves with randomly distributed phases is handled very clearly. The following two §§ 2.5 and 2.6 acquaint the reader with harmonic analysis; moreover, in § 2.6 the Fourier decomposition of finite, almost monochromatic wave trains is considered, and thus the reader is prepared for very many important questions of physical optics—in particular, the question of the width of spectral lines, so unsuccessfully presented in Monk’s book. Chapters III—“Interference of Two Beams of Light”—and IV—“Interference in Multiple Reflections”—are also very good. Chapters V–VIII deal with diffraction; here the authors—according to the amount of space devoted—quite correctly begin with Fraunhofer diffraction and devote three chapters to it (V, VI, VII), and at the end, in Ch. VIII, set forth the basic phenomena of Fresnel diffraction. It is worth dwelling somewhat on these chapters, since they seem to us exemplary. In Ch. V—Diffraction by a Single Slit—after a classification of phenomena the chief experiment on diffraction by a slit (§ 5.2) is considered, illustrated by a photograph in Fig. 5. Further the question is studied first analytically, with the results illustrated by good graphs, and then by means of the graphical method of summing amplitudes. In §§ 5.5 and 5.6 a rectangular diaphragm is considered and from it Rayleigh’s criterion of resolving power is elucidated, which is then (§ 5.7) applied to a prism. Finally, §§ 5.8, 5.9, 5.10 consider the circular diaphragm and the resolving power of an astronomical telescope and a microscope.

In Chapter VI diffraction by two slits is very appropriately considered in detail, and the difference between interference and diffraction is clearly brought out. Instructive photographs and graphs in Figs. 5, A and 6 E illustrate the influence of the widths of the slits and of the distance between them on the diffraction pattern. In § 6.8, with the aid of the lucid Fig. 6.9, the role of the finite width of the source is explained, and in § 6.9 Michelson’s stellar interferometer is described. Finally, in Ch. VII the diffraction grating and all the features of diffraction spectra (superposition of spectra, blazes, etc.) are considered.

After a well-composed chapter on the speed of light, including the optics of moving media, the authors proceed to the electromagnetic theory of light. Thereafter sources of light and their spectra, absorption, and scattering are considered. A special chapter is devoted to dispersion. Polarization, double refraction (including an exposition of the theory of propagation of electromagnetic waves in an anisotropic medium), and optical activity are presented with great clarity in the four following chapters (XIV–XVII). In Ch. XVIII

the electromagnetic theory of reflection and refraction is given, and in Chapter XIX—magneto- and electro-optical phenomena (the Zeeman, Faraday, Kerr effects, etc.). Each chapter is accompanied by questions and problems, and demonstration experiments are described in the text.

On the whole, this is an excellent, up-to-date book. One may hope that it will be translated into Russian—and soon. The appearance of such books greatly facilitates the work of both student and teacher and noticeably raises the standard of instruction.

E. Shpolsky. Moscow