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QC 351 A7 no. 74 / Measurements of the scattering of reflected light as a function of angular separation from the specular direction were made on aluminum-coated flat glass samples with surface roughnesses ranging from 1.0 nm to 70 nm rms deviation from the mean surface. Small -angle scatter (measured between 0.33° and 1° away from the specular direction) was investigated using light that had passed through a narrow slit; a measure of the scattering magnitude was provided by comparison of the far -field diffraction patterns produced by the slit, reflected from the samples and without the samples in place. The slit used to produce the diffraction patterns was optically processed to be smooth enough so that without the sample in place the minima of the diffraction pattern would be well defined and of lower magnitude than the scattered flux produced when the samples were in place. By considering the effects of the scanning aperture, it was determined that the measured magnitude of the minima agreed with those predicted by the use of Kirchhoff theory to within a factor of three. Comparison of small-and large-angle scatter measurements made on the same set of samples indicated that a transition region between the two types of scatter may exist in the region of 1° to 5° away from the specular direction. Because separate instruments were used for the small-and large-angle measurements, the results are expressed in terms independent of the measuring instrument's geometry. The measured results were compared to a theory in which the choice of the scatter function, and by implication the autocorrelation function, could be arbitrary. This comparison revealed that the choice of the hyperbolic secant function, rather than a Gaussian function, provided a good fit to the small-angle data. By fitting a curve to the small -angle data, it was possible to estimate the autocorrelation length of the surface roughness as well as the peak value of the scattering profile. The scatter measurements for the smoothest sample ranged from approximately 3 X 10' per µsr near the specular direction to 10 -13 per µsr at wide angles. For the roughest sample, the range was from 3 X 10-4 per µsr to 10-10 per µsr.

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"A novel approach to a light scattering experiment that employs a lounge image capture assay has been developed for both static and dynamic measurement on a wide variety of samples. In this work, the 'Development and Application of an Area Recorded Generalized Optical Scattering Technique', abbreviate as ARGOS, an approach is based on the placement of a translucent screen where the scattered light, now converted to a diffuse light, is imaged as a function of time. The placement and size of the screen determines the range of scattering wave-vectors, while the time between images determines the fastest dynamic resolvable . The overall experimental stability determines the slowest dynamic resolvable and so can be made arbitrarily long. The scattering intensity is measured by a camera whose dynamic range (number of bits per pixel), resolution, and speed determines the sensitivity and accuracy of intensity of the scattered light. The system allows for an extremely well-defined scattering experiment geometry, where images may be manipulated to extract structure (i.e. average I(q)over t) and dynamics (average I(q,t) over q) for a wide range of samples(liquids and solids). A number of innovation were developed. Instead of a beam stop to block the high intensity thru-beam, a thru-beam attenuator was developed such that the exact center of the scattering geometry is determined for each image acquired. A variety of image processing algorithms were also developed to correct for dead pixels, camera response, and intensity normalization. Of particular use was the development of the root-mean-square difference(RSD) image to probe dynamic. Here, the first image is taken as the time-zero reference image and subtracted from all succeeding images where averaged over a speci ed q and plotted as a function of time revealing the build up image changes due to dynamics. The technique was validated for both static and dynamic measurements with a set ofdilute suspended latex spheres in water (sizes ranging from 0.01 to 2micro m). The static light scattering result in terms of particle radius and dimension closely matched the expected values. The dynamic light scattering results could only several the end of the dynamics of these suspended latex spheres due to Brownian motion because of the speed limitation of the camera. However, sedimentation dynamics that are much slower, were early observed. The ARGOS technique was then applied to two biological systems, the evolution of a dilute suspension of E. Coli bacteria through the life-cycle and the evolution of the same suspended bacteria but infected with the MS2 bacteria-phage virus. High temporal resolution data were obtained of the bacteria life-cycle which werecorrelated with size, structure, and dynamics that revealed potentially new insights on behavior not well understood in the literature . The MS2 infected bacteria revealed the effect of the bacteria-phage on every character of the E. Coli life-cycle. The successful development and implementation of ARGOS here has also revealed avenues to greatly improve the performance."

Wong Wan Yan = 光學中消光截面佯謬之解釋 / 黃蘊殷. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 58-60). / Text in English; abstracts in English and Chinese. / Wong Wan Yan = Guang xue zhong xiao guang jie mian yang miu zhi jie shi / Huang Yunyin. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Scattering of a Plane Wave by an Infinitely Long Cylinder --- p.4 / Chapter 2.1 --- Dielectric cylinder (with no absorption) --- p.8 / Chapter 2.2 --- Perfectly conducting cylinder --- p.10 / Chapter 3 --- Scattering of a Gaussian Beam by a Dielectric Cylinder (Non- Resonance) --- p.13 / Chapter 3.1 --- Configuration and equations used --- p.13 / Chapter 3.2 --- Numerical result and discussion --- p.17 / Chapter 3.2.1 --- a <w --- p.19 / Chapter 3.2.2 --- a>w --- p.21 / Chapter 4 --- Scattering of a Gaussian Beam by a Dielectric Cylinder (Res- onance) --- p.24 / Chapter 4.1 --- Algorithm --- p.26 / Chapter 4.2 --- Numerical result and discussion --- p.28 / Chapter 5 --- Scattering of a Plane Wave by a Conducting Strip --- p.33 / Chapter 5.1 --- Configaration and equations used --- p.34 / Chapter 5.2 --- Numerical calculation --- p.39 / Chapter 5.3 --- Numerical results and discussion --- p.42 / Chapter 6 --- Actual Scattering Cross Section --- p.49 / Chapter 6.1 --- Configaration and Equations used --- p.49 / Chapter 6.2 --- Numerical result and disscusions --- p.51 / Chapter 7 --- Conclusions --- p.56 / Bibliography --- p.58 / Chapter A --- Bessel functions --- p.61 / Chapter B --- A plane wave incident on a single-layered medium --- p.63

Ng, Kin Sang = 球狀液滴的彈性光散射,包括高階彩虹、炫光點及形態相關共振的數值計算與實驗研究 / 吳健生. / Thesis submitted in: October 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 101-104). / Text in English; abstracts in English and Chinese. / Ng, Kin Sang = Qiu zhuang ye di de tan xing guang san she, bao kuo gao jie cai hong, xuan guang dian ji xing tai xiang guan gong zhen de shu zhi ji suan yu shi yan yan jiu / Wu Jiansheng. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Brief history --- p.1 / Chapter 1.2 --- The theory of rainbow --- p.4 / Chapter 1.2.1 --- Rainbow position --- p.4 / Chapter 1.2.2 --- Airy theory --- p.6 / Chapter 1.3 --- Glare points --- p.9 / Chapter 1.4 --- Mie scattering theory and Debye series --- p.11 / Chapter Chapter 2 --- Interference of the nth- and higher-order rainbows --- p.16 / Chapter 2.1 --- Introduction --- p.16 / Chapter 2.2 --- Interference of overlapping rainbows --- p.18 / Chapter 2.3 --- Results and discussion --- p.20 / Chapter 2.3.1 --- Glare point intensity of group G(ll) --- p.20 / Chapter 2.3.2 --- "Glare point intensities of groups G(8), G(9), and G(10)" --- p.24 / Chapter 2.3.3 --- Effects of varying acceptance angle --- p.27 / Chapter 2.3.4 --- Comparison with results of Lock and Woodruff --- p.29 / Chapter Chapter 3 --- Glare points of high-order rainbows --- p.30 / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- Results and discussion --- p.32 / Chapter 3.2.1 --- Glare points formed by rainbows of a particular order --- p.32 / Chapter 3.2.2 --- Glare points obtained by plane wave calculation --- p.42 / Chapter Chapter 4 --- Elastic light scattering from droplets embedded in gelatin --- p.45 / Chapter 4.1 --- Introduction --- p.45 / Chapter 4.2 --- Motivation --- p.48 / Chapter 4.3 --- Experimental Preparations --- p.51 / Chapter 4.3.1 --- Sample preparation --- p.51 / Chapter 4.3.2 --- Measurement of refractive index of gelatin --- p.53 / Chapter 4.4 --- Observation of morphology-dependent resonances by varying wavelength of incident laser light --- p.56 / Chapter 4.4.1 --- Experimental setup --- p.56 / Chapter 4.4.2 --- Results and discussion --- p.58 / Chapter 4.5 --- Observation of morphology-dependent resonances by varying temperature of droplet --- p.70 / Chapter 4.5.1 --- Experiment --- p.70 / Chapter 4.5.2 --- Results and discussion --- p.73 / Chapter 4.6 --- Scattered light intensity as a function of scattering angle --- p.77 / Chapter 4.6.1 --- Experiment --- p.77 / Chapter 4.6.2 --- Results and discussion --- p.79 / Chapter Chapter 5 --- Conclusion and future outlook --- p.89 / Appendix Program dave.for Listing --- p.92 / References --- p.101

M.S. / Applied Physics / The theory of stimulated Rayleigh-wing scattering in anisotropic molecular liquids is discussed. This theory is extended to include liquid mixtures. When binary mixtures are considered, a singularity is found in the threshold condition in certain circumstances. This leads to the possibility of measuring the anisotropic polarizability difference for one of the liquids. In addition, the appearance of the singularity suggests a method of determining whether saturation plays an important role in stimulated Rayleigh-wing scattering.

Flocculation is an important part of the carbon cycle. It is therefore crucial to understand how flocculation is regulated and how different environmental factors impact. A dilemma is that it has been found difficult to measure flocculation experimentally. In this thesis, flocculation of dissolved organic carbon in a Swedish lake was measured in a series of laboratory experiments. The method used was Dynamic Light Scattering (DLS). DLS is used to determine the size distribution profile of, for instance, small particles in suspension. DLS measures Brownian motion and relates it to the particle size by measuring the fluctuation in scattering intensity. It is not very effective to measure the frequency spectrum contained in the intensity fluctuations directly, so instead, a digital auto correlator is used. Since factors such as pH, salinity and calcium chloride content varies in lakes and is thought to have an impact on flocculation, this was investigated as well. As pH was changed in a range of 3 to 9, small changes in size distribution could be detected. Salinity and calcium chloride content have quite an impact on flocculation. Time also has a great impact, samples that were set to rest for a week showed a significant increase in particle size. For DLS to work, the samples need to be filtered of centrifuged to get rid of large particles. Different types of filters were tested to see which filter material was the best to use. When filtering the water we only want to filter out the large particles. Natural organic matter has a hydrophobic component which adsorbs to some filter types but not to others. It is crucial to know which filters this hydrophobic component adsorbs to, so that the loss of dissolved organic carbon during filtration can be minimalized.

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