The scattering of a plane electromagnetic wave by a conducting circular cylinder

The uniform asymptotic solution of light scattering from a conducting circular cylinder at oblique incidence is derived by using the Watson transformation method. It clearly demonstrates that the major contributions of the total field are the Fresnel integrals in the transition regions, the creeping waves in the shadow region, and the incident wave and the reflected wave in the lighted region. The creeping wave is excited by the incident ray tangential to the surface of the cylinder, and it creeps further into the shadow region. The creeping wave can radiate energy tangentially away from the curved surface; hence it is a damped periodic wave.

A He-Ne laser was used as a light source, and the conducting cylinder was an aluminum-coated quartz fiber. The positions of intensity maxima and minima of the scattered light predicted by the uniform asymptotic solution were in good agreement with experiment. Although the uniform asymptotic solution is derived under the assumptions of high frequency and large radius, it still gives good results at relatively low frequencies, where the ratio of the radius to the wavelength is of the order unity. The uniform asymptotic solution has the advantages of simplifying the numerical calculation and of giving a physical model of the exact solution.