Redirection of a portion of the sound beam back to the transducer is known as

• A. Reflection
• B. Refraction
• C. Diffraction
• D. Scattering

Answer: (A)

When ultrasound energy hits a boundary with a change in acoustic impedance, part of the wave is redirected back toward the transducer. This returning energy, or echo, is what the transducer detects to form the image. That redirection back toward the source is called reflection. Refraction would be the bending of the beam as it enters a new medium, not return to the transducer. Diffraction refers to bending around obstacles or openings, and scattering describes energy dispersed in many directions due to small structures—though some energy may reflect, the defining feature of the described process is the beam being sent back to the transducer, i.e., reflection.