Bibliography

D. N. Lazarev. Ultraviolet Radiation and Its Applications. State Energy Publishing House. Leningrad—Moscow, 1950, 119 pp., 71 figs. Bibliography: 25 titles. Price 5 rubles 75 kopecks. Print run 5000 copies.

In recent years the field of application of ultraviolet radiation has expanded enormously. Ultraviolet radiation has proved to be an effective means of destroying microbes (bactericidal lamps). The use of ultraviolet radiation in combination with luminophores has opened up new possibilities for decorative art in the theater and cinema. Finally, the use of ultraviolet radiation underlies the operation of fluorescent lamps. Therefore ultraviolet radiation is encountered by representatives of the most diverse professions, often very remote from physics and from optics in particular.

Poor knowledge of the optics of ultraviolet rays not infrequently leads to illiterate, technically irrational use of apparatus and hampers the development of this important branch of applied optics.

D. N. Lazarev’s book has as its aim to give a fairly broad circle of readers an idea of ultraviolet rays, their properties, and to promote the use of these rays in the most varied fields of technology and art.

The need for such a book has long been felt, and therefore there can be no doubt as to the correct orientation of the book. The purpose of the present review is to analyze how successfully the author has solved the correctly posed problems.

The first chapter of the book—radiant energy—is devoted to the basic characteristics of radiant energy and its receivers. Here simple but important information is given for persons working with sources and receivers of radiant energy (distribution of energy over the spectrum, photosensitivity). A classification of the spectral regions in the ultraviolet part of the spectrum is given separately. Here it would have been advisable also to indicate the other names of the three regions of the ultraviolet spectrum, in addition to those given in the book (far—short-wave, near—long-wave).

The second chapter—principles of radiation and sources of radiant energy. The chapter begins with a brief account of the laws of temperature radiation. On p. 15 a not entirely precise definition of an absolutely black body (a complete radiator) is given. It is said, without qualification, that “It is a hollow closed body with a small opening.” Earlier the discussion is of an ideal absolutely black radiator. Therefore the real black radiator is confused with the ideal absolutely black radiator.

It seems to us that in Fig. 5 (p. 16) (energy distribution) a logarithmic scale was chosen in vain for the ordinate axis. This deprives the curves of their usual appearance and makes the displacement law unclear. The distinction between gray and selective temperature radiators should have been emphasized in greater detail.

In presenting the questions of luminescence, it would have been possible not to include Fig. 11, showing deep-sea luminous animals, since it has little relation to the main subject of the book.

The mechanism of excitation of atoms in a discharge is described briefly, but quite correctly. Only the phrase on p. 24, “the intensity of its (the atom’s) feedback,” is somewhat unfortunate.

All the more regrettable is the gross physical error made by the author on p. 25 in attempting to explain the cause of the appearance of a continuous spectrum in temperature sources. The author sees the reason in the fact that “the molecules of a heated substance are excited as a result of the chaotic thermal motion of particles.” At the same time the words of S. I. Vavilov are quoted in such a way as to create the impression that he too shared this point of view. Of course, the quotation from S. I. Vavilov’s work has no relation to the character of the spectrum. The author evidently does not suspect that heated vapors and gases emit a line spectrum rather than a continuous one, and that the appearance of a continuous spectrum in heated solid bodies is connected with the interaction of elementary emitters. This error is substantial, since one of the main sources of ultraviolet radiation—a high-pressure mercury lamp—is essentially a temperature radiator (of which the book says nothing).

Specific data on mercury lamps are given in a form convenient for practical purposes.

The question of the radiation output of “bactericidal lamps” can only cause bewilderment in the reader. On p. 25 it is said that these lamps emit “about 70% of their energy in the form of homogeneous radiation of 254 mμ.” It is not clear what is meant by “their energy”—the power of the lamp or the radiated power of the lamp.

As Table 3 on p. 26 shows, the radiation output of bactericidal lamps is considerably below 70% (in the spectral, radiation, flux sphere). Alongside Table 3 for bactericidal lamps and Table 5 for mercury lamps (p. 29), such a table should also have been given for super-high-pressure lamps. The optical properties of SHP lamps are in no way characterized in the book. The following chapters are devoted to separate areas of application of ultraviolet radiation. In doing so, the author pursues the idea advanced by him at the beginning of the book, of the usefulness of measuring radiant energy with the aid of selective receivers. The spectral sensitivity of such receivers must correspond to the spectral characteristic of the object upon which the ultraviolet radiation acts in the given specific practical installation. This direction of technical measurements of radiant energy is presented to us as a reasonable generalization of the method of visual photometry (where the eye serves as the selective receiver). The use of luminophores for these purposes, described in the book, is also reasonable. The author can only be reproached for ignoring certain domestic works that were pioneering in the application of luminophores for measuring ultraviolet radiation. The question of methods for measuring erythemal radiation should also have been covered more specifically. For some reason, preference in this respect is given to bactericidal radiation.

A useful attempt is made to illuminate questions of the design of irradiating installations. These are, in essence, the beginnings of the lighting engineering of the ultraviolet. The data on the biological effectiveness of ultraviolet are very interesting, but do not always give a reliable impression (p. 33).

The fifth chapter—photoluminescence—serves to a considerable extent as preparation for the exposition of the last two chapters.

Here there is also brief fundamental information on the physical characteristics of the main types of luminophores and, along with this, some details of the technology of applying luminophores. Perhaps the high efficiency of the luminophores themselves, as converters of radiant energy, should have been noted.

Luminescent lamps are described briefly, but clearly. Along with the Hermitage, a photograph should have been provided of some existing, numerous installation for industrial lighting with luminescent lamps, and the undesirability of using open luminescent lamps should have been pointed out.

The last two chapters—“black light” and its application—bring together interesting material needed for the design and operation of “black-light” installations. The author proposes introducing a special unit of black irradiance (“chel”). Earlier the author proposed the “black lux” and was unsuccessful. It is possible that the “chel” will also prove not to be long-lived, but the systematization of measurements in this region (the near ultraviolet) is necessary.

Information on the application of “black light” is given in concise form and clearly pursues propagandistic aims. In this sense the book will play a positive role and will broaden the field of application of ultraviolet radiation. The decorative possibilities of “black light” have already been assessed by our theaters according to their merits. The use of luminophores in machine-tool painting still remains a highly debatable question.

At the end of the book a summary is given of quantities characterizing radiant energy, as well as a brief bibliography. One should note a certain carelessness in the terminology used by the author (not everything is in order with the dimensions of the quantities).

The book is illustrated with numerous figures and even has two color inserts, one of which vividly illustrates the advantages of Brumberg’s elegant microscopic method.

On the whole, the book will undoubtedly find its reader and will be useful to that reader.

V. A. Fabrikant