Answer #27

The correct answer is D: There are three main types: specular reflection, Rayleigh scattering and refraction. Refraction is not a type of reflection, it is an entirely different process where by differences in the velocity of travel within a medium changes the direction of propagation at an interface. The three main types are specular, backscattering and Rayleigh scattering. Rayleigh scattering occurs when the wavelength of the object is similar to that of the ultrasound. (Choice D) Specular reflection occurs when the object has a much larger wavelength than the ultrasound. The angle of incidence equals the angle of reflection and a mirror image is created. Good specular reflectors in the body include bones and tendons or large calcifications. Backscattering occurs when the a boundary has irregularities that are about the same size and the ultrasound wavelength.