T. L. Teng, F. T. Wu; A two-dimensional ultrasonic model study of compressional and shear-wave diffraction patterns produced by a circular cavity. Bulletin of the Seismological Society of America ; 58 (1): 171–178. doi:
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Diffraction patterns of compressional (P) and shear (SV) waves produced by a circular hole were experimentally obtained on a two-dimensional ultrasonic model. The shapes of the Fresnel patterns were found to depend on, 1) α/λ, the ratio of the radius of the cylinder to the wavelength; and, 2) the wave type. The transitional zone between the illuminated and the shadow regions broadens, and the half-amplitude point shifts away from the geometrical shadow as α/λ decreases. For comparable α/λ, the shadow boundary of the SV wave appears to start much earlier than that of the P wave.