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Earth and Space Sciences · 术语表

什么是 Fresnel zone？

Definition 2.8 University Earth and Space Sciences — Year 3 · 第 2 章 — Exploration Seismology

The (first) Fresnel zone of a reflector, for a coincident source and receiver at height $z$ above it, is the disc of reflector around the normal-incidence point from which the two-way path is longer than the normal path by less than half a wavelength: its reflections arrive in phase and build the recorded reflection together.

The first Fresnel zone (schematic): the part of the reflector whose distance from a coincident source and receiver exceeds the normal distance z by less than /4 (dashed arc: the sphere of radius z + /4), so that the two-way excess path is under half a wavelength and its echoes arrive in phase. The scale of is exaggerated. — The first Fresnel zone (schematic): the part of the reflector whose distance from a coincident source and receiver exceeds the normal distance $z$ by less than $\lambda/4$ (dashed arc: the sphere of radius $z + \lambda/4$ ), so that the two-way excess path is under half a wavelength and its echoes arrive in phase. The scale of $\lambda$ is exaggerated.

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