Convergence correction in colloid scattering
- 18 Downloads
The error introduced in depolarisation measurements due to the convergence of the incident beam has been investigated theoretically as well as experimentally for the case of colloid scattering, where the particles are not small compared to the wavelength of light. Assuming the scattering particles to be anisotropic rods, it is shown that, when the incident unpolarised light is condensed by means of a lens with a circular aperture, the observed depolarisation ratio ϱu is given by ϱu = ϱu0 + 5/3 θ2 where ϱu0 is the true depolarisation for incident parallel light, and θ the semi-angle of convergence. Appropriate formulae are derived when the incident beam is polarised vertically and horizontally. Experiments performed on six typical colloids support the theoretical conclusions. Other immediate consequences of the theory are also discussed.
Unable to display preview. Download preview PDF.
- 1).Ananthakrishnan, R., Proc. Ind. Acad. Sci. A2, 133 (1935).Google Scholar
- 2).Cabannes, J., Ann. de Phys.15, 113 (1921).Google Scholar
- 3).Gans, R., Physik Z.28, 661 (1927).Google Scholar
- 4).Ramanathan, K. R. andN. G. Srinivasan, Phil. Mag.1, 493 (1926).Google Scholar
- 5).Rao, I. R., Indian J. Phys.2, 72 (1927).Google Scholar
- 6).Rocard, Y., Compt. Rend.182, 690 (1926).Google Scholar
- 7).Vijaraghavan, K. andR. S. Krishnan, J. Indian. Inst. Sci.36A, 1 (1954).Google Scholar
- 8).Horn, P., Ann. de Phys.10, 386 (1955).Google Scholar
- 9).Krishnan, R. S., Proc. Ind. Acad. Sci. A5, 499 (1937).Google Scholar
- 10).Sivarajan, S. R., Thesis (1954).Google Scholar