Specular reflections are produced by surfaces with which characteristics?

• A. Rough surfaces
• B. Irregular surfaces
• C. Small and narrow features
• D. Large and smooth surfaces

Answer: (D)

Specular reflections come from surfaces that are smooth and large relative to the ultrasound wavelength. When a wave hits a smooth, flat interface, it reflects in a single direction with the angle of reflection equal to the angle of incidence, like a mirror, producing a bright, well-defined echo. If the surface is rough or irregular on the scale of the wavelength, the sound reflects in many directions from microscopic facets, creating diffuse echoes and a grainy or speckled appearance rather than a clean, specular image. Very small features also fail to produce a coherent mirror-like reflection because they scatter the beam in multiple directions instead of reflecting it coherently. So a large, smooth surface best yields specular reflections.