Rectilinear Propagation Of Light Research Articles

Effects of Ray Bending in Scattered Light Photoelasticity for Tempered and Annealed Glass Plates

Residual stresses in tempered glass plates can be measured with the scattered light method. Usually a rectilinear propagation of light is assumed. However, due to the gradients of the refractive index, the light rays curve. We have experimentally demonstrated this for tempered (surface stress 120 MPa and more) and annealed glass plates. For a laser beam of finite width this also results in broadening and loss of photoelastic modulation. While some features of the experimental picture (dependence of the period of modulation on depth), can be captured in the simple model of rectilinear propagation, the other observations need development of more elaborated models.

Geometry of Light and Shadow: Francesco Maurolyco (1494–1575) and the Pinhole Camera

Summary In his Theoremata de lumine, et umbre (1521), Francesco Maurolyco (1494–1575) discussed, inter alia, the problem of the pinhole camera. Maurolyco outlined a framework based on Euclidean geometry in which he applied the rectilinear propagation of light to the casting of shadow on a screen behind a pinhole. We limit our discussion to the problem of how the image behind an aperture is formed, and follow the way Maurolyco combined theory with instrument to solve the problem of the projection of light through small apertures. We show that Maurolyco not only reformed the classical sources which, he thought, were no longer the authoritative code of textual knowledge, but also established with the dioptra a novel linkage of method, theory, and instrument. He thereby demonstrated the importance of optics to the science of astronomy.

Optics in the Age of Euler: Conceptions of the Nature of Light, 1700–1795 by Casper Hakfoort

968 Book Reviews TECHNOLOGY AND CULTURE his major contribution may be to remind us that inventions are the creation of discrete content as well as cognitive process, of local knowledge as much as blinding insight. William S. Pretzer Dr. Pretzer, director of educational programs at Henry Ford Museum & Green­ field Village, recently completed a term on the National Commission for Technology Education, a K-12 educational standards project. Optics in the Age ofEuler: Conceptions ofthe Nature ofLight, 1700-1795. By Casper Hakfoort. Cambridge: Cambridge University Press, 1995. Pp. 243; figures, tables, notes, bibliography, index. $64.95 (hardcover). There is a considerable literature on the debate on the nature of light, and historians of science agree that until the 19th century the corpuscular (or emission) theory of light had the upper hand. The main purpose of this book, as stated by its author, is to “enrich and qualify” this picture by showing that in Germany in the second half of the 18th century Leonhard Euler’s wave theory was preferred to the corpuscular theory. This conclusion is based on a comprehensive study (apparently the first one) of the dispute on the nature of light in Germany. This is the strongest part of the book and provides a wealth of informa­ tion little known even to historians. Hakfoort also attempts to revise the generally accepted outline of the controversy on the nature of light, in particular, the view that the opposition between “the emission and medium traditions” de­ veloped in the second halfof the 17th century. In his view this oppo­ sition emerged after Euler. To prove this point, the author gives a detailed account of Euler’s theory, which he believes to be the first wave theory of light (however, see below), and discusses the German response to it. Finally, Hakfoort offers a new classification of the methodological components of science. In addition to mathematics (“classical tradi­ tion”) and experiment (“Baconian tradition”), used by Thomas Kuhn and others, he suggests a third, “theoretical natural philoso­ phy,” which refers to a qualitative explanation of phenomena. Hak­ foort claims that 18th-century optics was “torn among the three tra­ ditions” (p. 182), each of which developed different methods and objectives. In his view, only Huygens synthesized all three method­ ological components, while Newton’s optics was short on mathemat­ ics and Euler’s, on experiment. In the early 19th century, French researchers revived Huygens’ methodology so that “equal attention was given to all three of these elements” (p. 184). The author uses this scheme to account for the reception both of Newton’s theory TECHNOLOGY AND CULTURE Book Reviews 969 ofcolors and ofEuler’s theory and concludes that the lack ofcontact among “theory, mathematics, and experiment” (p. 188), prevented a more complete mathematization ofphysical optics in the 18th cen­ tury. In his view, the problem was not in applying mathematics but in finding “an integrated method” (p. 189). The book provides interesting observations about the work of Eu­ ler and others, although readers may disagree with some of the au­ thor’s conclusions, based on his own interpretations of terms or his­ toriographical issues. In particular, he treats optics before 1800 as dealing primarily with colors, and he begins the story of the wave theory with Euler because the only “true” waves, in his view, are the periodical ones. While Hakfoort is correct about Euler’s theory as the best contri­ bution to the “medium tradition” in the 18th century, to say that it was a “full-fledged alternative to the emission theories” (p. 115) is an exaggeration. Euler’s theory could not explain even phenomena already accounted for by Newton, such as rectilinear propagation of light, diffraction, colors of thin films, double refraction, and polar­ ization. For this reason, some historians do not consider Euler’s the­ ory to be an equal alternative to Newton’s emission theory (see, for instance, the paper by L. Minchenko in Physics at the Turn ofthe 17th18th centuries [in Russian] [Moscow, 1974]) While a formal mathe­ matical introduction of periodical waves was an achievement in it­ self, it remained useless for optics until the discovery of the principle ofinterference by Thomas Young, who borrowed the idea ofperiodi...

The logic of scientific and religious principles

In every domain, the philosopher finds some principle which is unfalsifiable in so far as all experience is interpreted in accordance with it. This principle is tautologous or analytic-within-its domain in that it defines fundamental terms with which it characterizes experiences: Newton’s Laws define “mass” and “the equality of times”; the Principle of the Rectilinear Propagation of LIght defines “light”; the Principle of Evolution defines “adaptation” and “natural selection”; and the Principle of the Conservation of Energy defines “a closed system.” Moreover, each principle is employed as a methodological rule or a tacit imperative to the investigator to interpret experience or to draw inferences in accordance with it. Nevertheless, each principle has empirical content: not only by virtue of its place within its respective domain but also because there are sufficient rules of correspondence which make the statement-form empirically relevant; not only because the principle itself is taken to be true but also because empirical inferences are drawn in accordance with it. To construe these principles as mere counterfactuals would be clearly incorrect. Counterfactuals, as Rescher would characterize them, are “belief-contravening suppositions” because certain beliefs are excluded if one is to be consistent. Although this is certainly true of these principles, the range of beliefs contravened is far larger than those beliefs excluded in mere laws of nature. For, to give up these principles would be to give up explaining the entire domain of experience to which they are applicable.

The influence of grid geometry on moiré fringe properties

General equations are developed which relate the characteristics of moiré fringes to the geometry of two superposed, dissimilar grid systems. Equations are derived geometrically, assuming the rectilinear propagation of light, and the analysis is restricted to a consideration of linear, periodic, mutually inclined systems. Criteria are established for the production of first and second order fringe systems, and some particular cases of grid geometry are examined in detail. The concepts of mixed grids and hybrid grid combinations are introduced, and the principles and possible applications of fringe sharpening, fringe multiplication and dual sensitivity systems are discussed.

Mirrors, Prisms, and Lenses: a Text-book of Geometrical Optics

THE revised edition of Prof. SouthalPs text-book of geometrical optics, in addition to a number of new problems scattered throughout the book, contains an important new chapter at the end of the volume. The historical notes dealing with the rectilinear propagation of light, and optics in the seventeenth century are of considerable interest. It is usually stated that Newton was the first to distinguish seven colours in the prismatic spectrum, but Maurolycus (1575) in the explanation which he gave of the circular arc of the rainbow directs attention to the four principal colours, together with three other colours which he regarded as transitions. Reflection prisms are discussed at some length, and new and approved schemes of optical calculation, partly due to Mr. T. Smith, are described. A word of praise must be given to the diagrams.