Occurs when the reflector is smaller than the wavelength of the sound beam

Occurs when the reflector is smaller than the wavelength of the sound beam

• A. Specular reflection
• B. Rayleigh scattering
• C. Refraction
• D. Backscatter

Answer: (B)

When a reflector is much smaller than the wavelength, the scattered sound follows Rayleigh scattering. In this regime, the incident wave interacts with the tiny object as a point-like source, so energy is radiated in many directions rather than reflected in a single, mirror-like beam. The backscattered signal tends to be weaker and more isotropic, and its strength increases rapidly with frequency (roughly with the fourth power of frequency). This distinguishes it from specular reflection, which requires a surface larger than the wavelength and directs energy back toward the transducer, and from refraction, which is bending of the beam at a boundary with different speeds. Backscatter is the general return of energy to the transducer, but Rayleigh scattering specifically describes the small-particle case.

When a reflector is much smaller than the wavelength, the scattered sound follows Rayleigh scattering. In this regime, the incident wave interacts with the tiny object as a point-like source, so energy is radiated in many directions rather than reflected in a single, mirror-like beam. The backscattered signal tends to be weaker and more isotropic, and its strength increases rapidly with frequency (roughly with the fourth power of frequency). This distinguishes it from specular reflection, which requires a surface larger than the wavelength and directs energy back toward the transducer, and from refraction, which is bending of the beam at a boundary with different speeds. Backscatter is the general return of energy to the transducer, but Rayleigh scattering specifically describes the small-particle case.