Summary
The scattering of an electromagnetic field by a small circular disc is investigated with the assumption that the disc can conduct current in only one direction. The analysis follows closely that given byBethe in a similar case. Although Bethe’s theory is open to criticism and leads to some wrong results, the present discussion appears to the author to be perfectly correct. Both the scattering cross-section and the angular momentum cross-section are evaluated. This is sufficient for explaining why the experimental measurement of the torque exerted upon the screen is in poor quantitative agreement with the theory based on the geometric cross-section.
Riassunto
Viene studiata la diffrazione di un’onda elettromagnetica da parte di un disco sottile, di piccolo diametro, perfettamente conduttore in una direzione e isolante nella direzione ad essa ortogonale. Si applica un metodo già seguito daBethe nel caso di un foro circolare in uno schermo perfettamente conduttore. Viene calcolata la sezione efficace di assorbimento di momento angolare. Viene dimostrato un teorema generate che mette in relazione questa sezione efficace con la sezione di scattering.
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References
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The present research was made in partial fulfillment of Contract AF 61 (514)-433 between the European Office of the Air Research and Development Command, United States Air Force, and the Centro Microonde del C.N.R.
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di Francia, G.T. Electromagnetic cross-section of a small circular disc with unidirectional conductivity. Nuovo Cim 3, 1276–1284 (1956). https://doi.org/10.1007/BF02785008
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DOI: https://doi.org/10.1007/BF02785008