A 45-degree shear angle beam transducer produces a wave in the metal that is polarized in which way?

• A. Perpendicular to the direction of propagation and at 45 degrees to the entry surface
• B. Perpendicular to the entry surface
• C. In the direction of propagation and at 45 degrees to normal to the entry surface
• D. Perpendicular to the direction of propagation and parallel to the entry surface

Answer: (A)

The main idea is that a shear wave’s particle motion is perpendicular to the direction the wave travels. For a 45-degree shear-angle beam, the ray path is 45° to the entry surface, so the transverse motion (polarization) ends up also at 45° to the surface. That makes the wave polarized perpendicular to the propagation direction and at a 45° angle to the entry surface.

This matches the description: polarization is perpendicular to the direction of propagation and at 45 degrees to the entry surface.

Why the other descriptions don’t fit: being perpendicular to the entry surface would imply a 90° relation to the surface, which isn’t the case for a 45°-incident shear beam; a wave polarized in the direction of propagation would be a longitudinal wave, not a shear wave; and being perpendicular to propagation but parallel to the entry surface is inconsistent with a 45° incidence.