What is the primary characteristic of Rayleigh waves?

Rayleigh waves are a type of surface wave that travel along the interface between a solid and a gas or a solid and a liquid. The primary characteristic of Rayleigh waves is that particle motion is elliptical. This means that as Rayleigh waves propagate, the particles in the material move in an elliptical path. This behavior is a result of the wave's surface nature, where it combines both longitudinal and transverse wave characteristics.

The elliptical motion of particles is significant because it affects how the wave interacts with materials, influencing factors like wave speed, amplitude, and the manner in which energy is distributed along the surface. This unique particle motion in Rayleigh waves is responsible for various applications in nondestructive testing, particularly in detecting surface-breaking defects in materials.

In contrast, linear, circular, or random particle motions do not accurately describe the behavior of Rayleigh waves, making them incorrect options in this context.