Which term refers to reflections that are angle dependent and occur as a single directional reflection?

• A. Reflection angle
• B. Refraction
• C. Scattering
• D. Specular reflections

Answer: (D)

Specular reflections occur when the boundary is smooth on the scale of the ultrasound wavelength, so the sound reflects in a single direction according to the angle of incidence equals the angle of reflection. This angle-dependent, mirror-like return is why you see a distinct echo from smooth interfaces, such as a fluid boundary or a polished surface. If the surface is rough or the structures are smaller than the wavelength, the energy scatters in many directions rather than returning in one direction—this is scattering. Refraction, by contrast, is the bending of the wave as it passes into a different medium with a different speed, involving transmission rather than a single reflected ray. The term “reflection angle” isn’t the standard descriptor here; the appropriate term for the angle-dependent, single-direction reflection is specular reflection.