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The interaction of
an oblique plane wave with an interface separating two fluid media
causes a reflected
wave in the medium 1 and a transmitted
wave in the medium 2.
The whole field in the medium 1, which is the summation of the incident and reflected fields, has always a stationary character in the direction perpendicular to the interface (following y), and a propagative character in the direction of the interface dans la direction de l'interface (following x). ![]() |
When the
propagation velocities c1 and c2
of the waves in media 1 and 2 are such that c1
< c2, there exists a value for the
incident angle
![]() ![]() ![]() The evanescent
transmitted wave
propagates in a direction parallel to the interface, while its
amplitude has an exponential decreasing with the depth (when y
increases), in a direction perpendicular to the interface.
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The
cartographies below represent the amplitude of the real part of the
acoustic pressure; color level (red = maximum, blue = minimum). The oblique black lines represent incident, reflected and transmitted rays, as they are predicted by Snell-Descartes' laws: when the transmitted wave is propagative ( ![]() ![]() |
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Incident angle inferior to the
critical angle
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Incident angle superior to the
critical
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Incident angle equal to the
critical angle
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