by Ng Pak Hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 111-112). / Text in English; abstract also in Chinese. / by Ng Pak Hong. / Acknowledgments --- p.i / Abstract --- p.ii / Table of contents --- p.iv / Chapter Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- History --- p.2 / Chapter 1.2 --- Airy Theory --- p.4 / Chapter 1.2.1 --- Rainbow angle --- p.4 / Chapter 1.2.2 --- Airy's cubic wave front --- p.4 / Chapter 1.3 --- High-order rainbows --- p.7 / Chapter 1.4 --- Glare points --- p.8 / Chapter 1.5 --- Interference between overlapping rainbows --- p.10 / Chapter Chapter 2 --- HIGH-ORDER RAINBOWS --- p.17 / Chapter 2.1 --- Experiment --- p.17 / Chapter 2.2 --- Results and discussions --- p.19 / Chapter 2.2.1 --- General features --- p.19 / Chapter 2.2.2 --- Angular positions and angular widths of rainbows --- p.21 / Chapter 2.2.3 --- Rainbow intensities as functions of order number --- p.22 / Chapter 2.3 --- Vertical positions of rainbows --- p.24 / Chapter 2.4 --- Vertical spreads of rainbows --- p.26 / Chapter 2.5 --- Rainbow patterns at different values of the refractive index ..… --- p.28 / Chapter 2.6 --- Effect of eccentricity of a droplet's circumference in the equatorial plane on the rainbow angles --- p.30 / Chapter CHAPTER 3 --- GLARE POINTS --- p.56 / Chapter 3.1 --- Experiment --- p.56 / Chapter 3.2 --- Results and discussions --- p.57 / Chapter 3.2.1 --- General features --- p.57 / Chapter 3.2.2 --- Glare point position and intensity --- p.58 / Chapter A. --- Glare point position --- p.58 / Chapter B. --- Glare point intensity --- p.61 / Chapter C. --- Summary of results of glare points --- p.62 / Chapter 3.2.3 --- Fourier transform of rainbow patterns --- p.63 / Chapter Chapter 4 --- INTERFERENCE BETWEEN OVERLAPPING RAINBOWS --- p.90 / Chapter 4.1 --- Experiment --- p.90 / Chapter 4.2 --- Results and discussions --- p.91 / Chapter 4.2.1 --- General features --- p.91 / Chapter 4.2.2 --- Simulation of the interference --- p.91 / Chapter 4.2.3 --- Estimation of the droplet vibration amplitude and frequency --- p.95 / Chapter 4.3 --- Comparison with results of Lock and Woodruff --- p.96 / Chapter Chapter 5 --- CONCLUSION --- p.107 / APPENDIX A --- p.109 / References --- p.111

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 339-359). Also available via the Internet

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A new wave-kinetic numerical method for the propagation of optical waves in weakly inhomogeneous media is discussed, and it is applied to several canonical problems: the propagation of beam and plane waves through a weak 3-D ( or 2-D ) Gaussian eddy. The numerical results are also compared to those from a Monte-Carlo simulation and the first Born approximation. Within the validity of the Liouville approximation, the Wigner distribution function ( WDF ) is conserved along the conventional ray trajectories, and, thus, by discretizing the input WDF with Gaussian beamlets, we can represent the output WDF as a sum of Gaussians, from which irradiance can be obtained by analytical integration of each Gaussian with respect to wavevector. Although each Gaussian beamlet propagates along a geometrical optics ray trajectory, it can correctly describe diffraction effects, and the propagation of optical waves through caustics or ray crossings. The numerical results agree well with either the Monte-Carlo method or the first Born approximation in regions where one or both of these are expected to be valid. / M.S.

This dissertation is an interdisciplinary study of scientific change. The undulatory theory of light replaces the emission theory of light in the early nineteenth century, triggering an "optical revolution" and vigorous debates among physicists in British from the 1830s to the 1850s. In this study I give the first full account of this extended episode of scientific change, drawing on methods and concepts from history, sociology and philosophy of science. The interdisciplinary account of the episode provides a basis for criticizing the existing models of scientific change in the philosophy of science. Previous historical studies of the “optical revolution" pay little attention to the period after the 1830s. Because the cognitive superiority of the undulatory theory had become obvious in the early 1830s, some historians have implicitly assumed that any controversy would soon come to a natural end. I, however, document that intensive debates continued from the 1830s until the end of the 1850s, and that emissionists even enjoyed temporary victories in their fights with undulationists. The narrative reveals the historical complexities of this episode: the debates extended long after the cognitive superiority of the undulatory theory should have become apparent by modern standard, the results of the debates did not necessarily coincide with modern cognitive judgements, and individual agents played decisive roles in determining how long a debate lasted and how it would end. On the basis of the historical narrative, I provide a philosophical analysis of the practices of theory appraisal and experiment appraisal that constituted the main theme of the controversy. Instead of merely identifying the criteria of evaluation employed in this episode, I pay special attention to how individual agents actually applied these criteria in concrete situations, what kinds of strategies or tactics they employed for the applications of these criteria, and how they created favorable conditions, both cognitive and social, for successfully applying these criteria. Individual agents’ efforts in selecting application strategies and in creating favorable conditions made the practices of appraisal complicated, exhibiting various features that are incomprehensible if we limit ourselves merely to studying the criteria of evaluation. I finally discuss a different approach to scientific change. The existing philosophical models of scientific change merely analyze the final product of science -- scientific theories, and ignore the impact of social factors and the role of individual agents. I suggest we concentrate on the process of knowledge production, and pay attention to individual agents’s practices in this process, as well as to the relevant cognitive and social factors that influence individual agents. Following this new approach, scientific change is understood as an evolution that involves interactions among three elements: theory, experiment, and human agent. / Ph. D.

The large-scale use of artificial light throughout the night has occurred in the last 100 years and continues to increase globally. Artificial light impacts many animal and plant taxa. The effects of artificial light on bats is species specific. The Namib Desert in Namibia is still relatively dark but subject to the same drivers of increasing development and urbanization that have increased the spread of artificial light globally. This study investigated the effects of the introduction of ultraviolet, yellow and white artificial light on the activity of bats in a rural environment with minimal development in the Namib Desert. Four sites, 100 m apart, had one light and one bat detector each. The fourth light was a dark control. Each site was sampled four times by each light type. Bat activity was recorded by the bat detectors. Eight bat species were recorded during the experiment. Activity increased for open air and clutter-edge foraging species analysed. Broadband white light caused the highest increases in activity followed by yellow light when compared with the dark control site. Ultraviolet light caused the lowest increases in activity contrary to expectations. / Mengwaga ye 100 ya go feta go bile le koketšego ye kgolo ya tšhomišo ya seetša sa maitirelo bošego ka moka. Setlwaedi se se ata kudu lefaseng ka moka go feta pele, gomme se ama diphoofolo tše ntši le mehuta ya dimela. Leganata la Namib go la Namibia gabotse le sa ntše le swiswetše, eupša le ka fase ga dikgontšhi tša go oketša tlhabollo le toropofatšo tšeo di hlotšego koketšego tšhomišong ya seetša sa maitirelo lefaseng ka bophara. Dikhuetšo tša seetša sa maitirelo go memankgagane di fapana go ya ka mohuta. Nyakišišo ye e nyakišišitše dikhuetšo tša tsebagatšo ya seetša sa maitirelo sa go phadima, serolwane le se sešweu go modiro wa memankgagane ka tikologong ya nagaselegae ya go ba le tlhabollo ye nyane ka Leganateng la Namib. Seetša se setee le tithekethara e tee ya mankgagane di hlomilwe go le lengwe le le lengwe la mafelo a mane, a go arogantšhwa ka 100 m. Seetša sa bone se be se le taolo ya leswiswi. Lefelo le lengwe le le lengwe le dirilwe mohlala makga a mane ka mohuta wo mongwe le wo mongwe wa seetša. Modiro wa mankgagane e rekotilwe ka ditithekethara tša mankgagane. Mehuta ya mankgagane ye seswai e rekotilwe nakong ya eksperimente. Modiro wa mehuta ya sebakabakeng le ya go sela thobekgeng ye e sekasekilwego e oketšegile. Seetša se sešweu sa porotepente se hlotše dikoketšego tša modiro, sa latelwa ke seetša se se serolwane, ge se bapetšwa le lefelo la taolo ya leswiswi. Go fapana le ditetelo, seetša sa go phadima se hlotše dikoketšego tša fasefase modirong. / School of Environmental Sciences / M. Sc. (Nature Conservation)