BIBLIOGRAPHY

R. W. Pohl, Introduction to Optics. Translated under the editorship of N. A. Tolstoy. State Publishing House of Technical-Theoretical Literature. Moscow—Leningrad, 1947, 484 pp., price 14 rubles.

The name of R. W. Pohl is well known to the Soviet reader from two of his earlier books: Introduction to Mechanics and Acoustics and Introduction to the Study of Electricity, which have gone through two editions and have become widely known. In these books the author treats the basic physical phenomena with great mastery, emphasizing a number of important and subtle questions (often omitted in ordinary university textbooks), approaching their interpretation in a non-stereotyped way and illustrating the exposition with original demonstration experiments.

Introduction to Optics is a valuable addition to the author’s previously published books, all the more useful because in the teaching of classical optics, especially geometrical optics, a rather strong stereotyped approach is felt, which is quite harmful to the essence of the subject.

In its construction, Introduction to Optics differs from the above-mentioned books in that a considerable part of the book, devoted to the study of the interaction of light with matter and to questions of radiation (especially Chapters 10–13), contains very extensive material that goes far beyond the limits of a course in experimental physics, but is very poor in experiments, which constituted the chief value of the first two books. Judging from the remark made by him in the preface, the author himself felt that these chapters fall outside the general plan of his book.

Chapter 1 is devoted to reflection and refraction; it is introductory and contains no particularly original material.

Chapters 2–4, devoted to the formation of images by means of lenses and to the role of apertures limiting a light beam, are of exceptional interest. The author sharply polemicizes against stereotyped methods of presenting geometrical optics and illustrates his views with a number of excellent experiments.

Particularly good is the experiment (§ 26) in which an image is obtained of two objects located at different distances from the lens, the size of the images changing depending on the position of the diaphragm that limits the beams participating in the formation of the image. Unfortunately, in Fig. 121, which explains the experiment, the distance is incorrectly indicated as 30 cm (apparently it should be 40 cm), or else the optical power of the lens is incorrectly specified.

Also very convincing are the experiments with the imaging of a point grating in the presence of a diaphragm (§§ 13, 14).

In Chapter 5, which deals with interference, the author analyzes in detail the question of the dimensions of the light beam permissible for carrying out interference experiments, and arrives at excellent experiments that make it possible to observe a pattern of Fresnel interference covering an entire wall (§ 40). For every lecturer demonstrating interference with the aid of mirrors or a Fresnel biprism, which produce an interference

picture within a very small angle with a negligible amount of light, the experiments described by the author afford much joy.

In considering diffraction (Chapter 6) the author does not present any original experiments. But the physical content of the usual diffraction demonstrations is analyzed with great clarity.

In Chapter 7, which deals with the velocity of light, there are no original experiments; the exposition also is not distinguished by novelty.

Polarization (Chapter 8) is, as is well known, one of the most difficult chapters of optics. The author examines polarization phenomena in detail, but, surprisingly, the exposition is not very rich in new opinions and experiments.

The demonstration of the position of the plane of oscillation of the electric vector in a polarized beam is witty (§ 71). The rotation of the plane of polarization is set forth very briefly. The well-known experiment of Umov, which produces an exceptional impression but is rarely mentioned in textbooks, is not indicated.

Chapter 9 is devoted to the question of the conditions under which light penetrates a substance and is completely internally reflected. Here there are several excellent experiments (§ 86), fresh ideas (which were absent in Pohl’s earlier books), and a large number of mathematical derivations hardly needed by the “beginning” reader for whom Pohl counts.

The same may be said of Chapters 10–13. Their original part will be read with great profit by a reader acquainted with the basic course of optics and wishing to deepen his knowledge. But for beginners these chapters are very difficult. An exceedingly effective experiment illustrates the propagation of light in a medium with a continuously varying refractive index (§ 109). But in general there are rather few experiments, and these chapters, which stand out from the general plan, are not characteristic of the author.

Chapter 14 concerns photometry and questions of the color of bodies and of luster. Here the “real” Pohl appears again, able dryly to criticize conventional pronouncements, to find new aspects in familiar phenomena, and to devise convincing, witty experiments (§§ 177, 179, 180, 183). Very valuable is the emphasis on the role of the psychological factor in the perception of color.

The book is produced satisfactorily; the translation is well done.

The editor of the translation has appended several notes establishing, in a number of cases, the priority of Soviet scientists, which, of course, is to be welcomed. However, the note on p. 301 is spoiled by a gross error: it says that combinational scattering in crystals was discovered by Raman, and in liquids by Landsberg and Mandelstam—an indication directly contrary to what actually occurred.

One cannot fail to regret also that instead of the term “incandescent light” introduced by Pohl—Glühlicht—the translator has retained the unfortunate term “white light” (although the light is rather “black” than “white”), specifically justifying (p. 14) its retention by saying that “the term has taken root.” It seems that a struggle against unfortunate terms is necessary. After all, “living force” was successfully abolished, dielectric constant was replaced by dielectric permittivity, self-induction of a coil by inductance, and so on, although all these terms had also “taken root.”

On the whole, Pohl’s book is of great value. It will be read with interest not only by students and secondary-school teachers, but also by workers in higher educational institutions. Lecturers who teach experimental physics will find in the book many valuable demonstrations, ingenious in conception and simple in execution, which can considerably enliven lectures on optics; and the ideas expressed by Pohl will compel many lecturers to reconsider some notions that have become too “settled.”

N. N. Malov