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contains, as a first approximation, the two-dipole model anticipated earlier[6]. It justifies the generality of the Bethe’s result for the case of a conical screen. Our model is in good agree- ment with the experimental data and explains in particular the backward emission found for the P-polarization. The angular transmission profile does not depend on the aperture radius for small holes, and is insensitive to the tip angle as long as it is smaller than 20 $^{◦}$. 

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[9] Bouwkamp C. J. and Casimir H. B. G., Physica, 20 (1954) 539. 

