Which statement best describes a property of shear or transverse waves used in ultrasonic testing?

• A. Particle motion normal to propagation direction, and velocity about 1/2 the longitudinal velocity
• B. Exceptionally high sensitivity due to low attenuation in water
• C. High coupling efficiency because shear waves are less sensitive to surface variables
• D. None of the above statements apply to shear waves

Answer: (A)

Shear waves are transverse in solids, so the particle motion is perpendicular to the direction of wave travel. Their speed is determined by the material’s shear modulus and density, and in most solids, the shear wave velocity is about half of the longitudinal (compressional) wave velocity in the same material. This combination of perpendicular particle motion and a slower, distinct velocity is what this description captures, making it the best match for describing shear waves in ultrasonic testing.

Note: shear waves do not propagate in liquids (like water) because liquids don’t support shear stress, so phrasing about low attenuation in water doesn’t apply to shear waves. The statement about coupling efficiency or surface-variables sensitivity isn’t a defining property of shear waves, whereas the perpendicular motion and the velocity ratio are the core characteristics.