What occurs when interface dimensions are much smaller than the wavelength?

When the dimensions of an interface are much smaller than the wavelength of the ultrasound being used, Rayleigh scattering occurs. This is a phenomenon where the scattering of waves happens by particles that are significantly smaller than the wavelength. In the context of ultrasound, when sound waves encounter small scatterers, such as red blood cells or other microscopic structures, the waves scatter in all directions.

Rayleigh scattering is particularly significant in medical ultrasound because it explains how sound interacts with small structures within the body, leading to the generation of echoes that can be detected and interpreted to create images. This scattering can enhance contrast in ultrasound images, especially in areas where small structures are present, separating them from the surrounding tissue.

Understanding Rayleigh scattering is crucial in sonography as it helps practitioners better interpret ultrasound images and understand the interactions between ultrasound waves and the tissues being examined.