Scattered light wavelength

The correlation fiinction G(/) quantifies the density fluctuations in a fluid. Characteristically, density fluctuations scatter light (or any radiation, like neutrons, with which they can couple). Then, if a radiation of wavelength X is incident on the fluid, the intensity of radiation scattered through an angle 0 is proportional to the structure factor... 

The term microemulsion was introduced by Schulman, who studied surfactant solutions as eady as 1943 (22). At that time it was widely accepted that "oil and water do not mix," and Schulman understood that an emulsion scatters light because it contains droplets whose diameters are large compared to the wavelength of light (see Emulsions). Thus, the term y /mJemulsion implies a system which (like an emulsion) contains droplets of oil or water, but in which the droplets are too small to scatter light. 

Compare the wavelengths of visible light with the range of pardde diameters which most efficiently scatter light. 

Raman spectrometry is another variant which has become important. To quote one expert (Purcell 1993), In 1928, the Indian physicist C.V. Raman (later the first Indian Nobel prizewinner) reported the discovery of frequency-shifted lines in the scattered light of transparent substances. The shifted lines, Raman announced, were independent of the exciting radiation and characteristic of the sample itself. It appears that Raman was motivated by a passion to understand the deep blue colour of the Mediterranean. The many uses of this technique include examination of polymers and of silicon for microcircuits (using an exciting wavelength to which silicon is transparent). 

Expt. no. Residual PVAc in porous film (%r Maximum wavelength of transmittance (nm) Color of scattered light... 

One of the characteristics of the porous film is that there is no effect on the film size in the solvents, despite the existence of PVAc, because of the enormous space taken up by the PVA cells versus the PVAc amount. If the porous film is dipped in a solvent, the PVAc concentration in the PVA cells may be appreciated by the residual PVAc amount. Because the refractive index of the PVAc solution in contact with PVA cells becomes lower as the amount of PVAc with a low-refractive index increases, the wavelength of the transmitted light for the porous film shifts to the short side, and the color of the scattered light shifts to the yellow side. This consideration successfully explains the experimental results in Table 4. 

Radiation from a xenon or deuterium source is focussed on the flow cell. An interchangeable filter allows different excitation wavelengths to be used. The fluorescent radiation is emitted by the sample in all directions, but is usually measured at 90° to the incident beam. In some types, to increase sensitivity, the fluorescent radiation is reflected and focussed by a parabolic mirror. The second filter isolates a suitable wavelength from the fluorescence spectrum and prevents any scattered light from the source from reaching the photomultiplier detector. The 90° optics allow monitoring of the incident beam as well, so that dual uv absorption and fluorescence... 

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