A study of electric dipole radiation via scattering of polarized laser light

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Physics and Astronomy


We have developed an advanced undergraduate experiment to explore electric dipole radiation in the optical frequency domain. A polarized laser beam is used to illuminate an aqueous suspension of skim milk, and the light scattered from the suspension is measured in the plane perpendicular to the laser beam as a function of the angle theta with respect to the polarization direction and as a function of the perpendicular distance R from the laser beam. When the length of the scattering region, d, is much smaller than R, the measurements agree very well with the sin(2) theta/R-2 dependence of electric dipole radiation. Increasing the scatterer concentration increases the background of multiply scattered light and decreases the degree of polarization of the scattered light with no appreciable change in the observed sin(2) theta/R-2 dependence. We discuss variations of the experiment for different instructional needs and describe how an understanding of dipole radiation helps students to appreciate a number of optical phenomena. (C) 2003 American Association of Physics Teachers.

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