Bibliography

Dr. Max Planck. Einführung in die theoretische Optik. Verlag von S. Hirzel in Leipzig, 1927. pp. VIII+184.

M. Planck. Introduction to Theoretical Optics.

Planck’s new book constitutes the fourth and final volume of the course Introduction to Theoretical Physics. The first part, Introduction to General Mechanics, is available in Russian translation and has probably already been duly appreciated by Russian readers. The second part is devoted to the mechanics of deformable bodies; the third, to electricity and magnetism. Introduction to Theoretical Optics may also be studied as an independent book; the references to the preceding volumes are sufficiently explained and cannot hinder a prepared reader.

In recent decades theoretical optics has been in a transitional state. A vast group of phenomena connected with the properties of light independent of matter, as well as with the action of matter upon light, find an almost exhaustive interpretation in the classical wave theory. Conversely, the action of light upon matter and the processes of the origin of light (spectroscopy) fit only into quantum theory. The synthesis of classical wave optics and quantum optics into a unified physical optics is a task for the future (probably not a distant one), but for the present there is no theory of light in the true sense that is both comprehensive and complete.

Planck’s course, like the other existing books on theoretical optics, deals only with the classical wave theory and the range of phenomena embraced by it; at the same time it differs substantially from its predecessors. Planck has succeeded in giving a very concise, yet extremely rigorous and simple exposition of the subject. It is enough to compare, for example, the widely used textbooks of Drude and Schuster with Planck’s book in order to see all the advantages of the latter.

The content of all these books is almost identical, but in Planck it is set forth in a volume approximately three times smaller than in Drude and Schuster. At the same time, the treatment of many fundamental questions (for example, the Huygens–Kirchhoff principle) is incomparably more rigorous and correct in Planck than in the above-named courses. Numerous brief remarks on the energy of a ray, on monochromaticity, coherence, etc., scattered throughout the book, greatly enliven the presentation of wave optics. Of course, the conciseness of the exposition will require of the reader a very attentive attitude toward almost every word of the book.

Schrödinger’s wave mechanics, in which one may with full justification see the first indication of a connection between wave and quantum optics, determines the general tendency of Planck’s course. In contrast to the accepted presentation, geometrical optics appears in Planck only in the third chapter, as a special case of wave optics. In the third part of the course, devoted to dispersion, Planck, in conclusion, touches on the geometrical optics of an inhomogeneous medium, introduces the concept of group velocity and, passing to the mechanical analogy, generalizes “geometrical mechanics” into Schrödinger’s wave mechanics. The constant \(h\) figures at first as a simple factor.

proportionality, and only at the end does Planck estimate the order of magnitude of \(h\) from atomic dimensions.

If Planck’s course is judged from the point of view of a theoretical researcher, then it is a necessary introduction and prelude to the understanding of modern wave mechanics.

S. Vavilov.