A P wave travels from steel ( ) into water ( ) at normal incidence

PHYSICS · Multi-part · Fermi University Physics · Oscillations, Waves & Acoustics · Fluids & Continuum Physics · Superposition, boundaries and interference

Bending, Ringing, Breaking and Flowing, Ch Elastic waves in a solid and at its surface

Problem

A P wave travels from steel (Z1=46.0 MRaylZ_1 = 46.0\,\mathrm{MRayl}) into water (Z2=1.48 MRaylZ_2 = 1.48\,\mathrm{MRayl}) at normal incidence. Someone argues: "The stress reflection coefficient is R=Z1−Z2Z1+Z2=46.0−1.4846.0+1.48=+0.938,R = \frac{Z_1-Z_2}{Z_1+Z_2} = \frac{46.0-1.48}{46.0+1.48} = +0.938, so the reflected stress pulse has the same sign as the incident one: a compressive pulse returns as compression." ((a)) Find the error in this working. ((b)) Give the correct stress reflection coefficient and state whether the reflected pulse is compression or tension.

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