Rayleigh waves are generated at the second critical angle.

Rayleigh waves are generated at the second critical angle.

• A. True
• B. False
• C. They are generated at the first critical angle
• D. They travel only in liquids

Answer: (A)

Rayleigh waves are surface-bound waves that travel along a free surface by coupling energy from bulk waves incident at the surface. When a bulk wave in the material strikes the surface at angles beyond a certain threshold—the second critical angle—the boundary conditions can no longer support the transmitted bulk waves in the same way, and the energy is converted into a Rayleigh wave that travels along the surface while its amplitude decays with depth. This is why Rayleigh waves are said to be generated at the second critical angle. Rayleigh waves move along the surface with particle motion in the plane of incidence and are highly sensitive to near-surface features, which is why they’re particularly useful in surface inspections. They are a solid-surface phenomenon—not something that travels only in liquids—and the notion that they occur at the first critical angle or that they exist only in liquids doesn’t fit the physical behavior of these surface-bound waves.

Rayleigh waves are surface-bound waves that travel along a free surface by coupling energy from bulk waves incident at the surface. When a bulk wave in the material strikes the surface at angles beyond a certain threshold—the second critical angle—the boundary conditions can no longer support the transmitted bulk waves in the same way, and the energy is converted into a Rayleigh wave that travels along the surface while its amplitude decays with depth. This is why Rayleigh waves are said to be generated at the second critical angle.

Rayleigh waves move along the surface with particle motion in the plane of incidence and are highly sensitive to near-surface features, which is why they’re particularly useful in surface inspections. They are a solid-surface phenomenon—not something that travels only in liquids—and the notion that they occur at the first critical angle or that they exist only in liquids doesn’t fit the physical behavior of these surface-bound waves.