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A description is given of an experimental study, using Bragg scattering, of the properties of cylindrically-focused longitudinal-wave acoustic beams in fused quartz in the frequency range 200–425 Mc/sec. The results are analyzed and shown to be in good agreement with Fresnel diffraction theory indicating, as expected, that elastic waves at ultrasonic frequencies, because of the extremely short wavelengths involved, propagate as coherent, unguided beams. This allows fabrication of simple focusing elements and makes available efficient light modulation structures as well as techniques for studying the properties of acoustic transducers.
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Cohen et al. (1967) studied this question.
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