What term describes the change in direction of a sound wave as it passes from one medium to another?

What term describes the change in direction of a sound wave as it passes from one medium to another?

• A. Reflection angle
• B. Refraction
• C. Spatial
• D. Temporal

Answer: (B)

Refraction is the bending of a sound wave as it crosses into a different medium because the wave travels at a different speed in each medium. In ultrasound, tissue interfaces have different speeds of sound (soft tissue around 1540 m/s, bone much faster), so when the wave hits the boundary at an angle, the change in speed causes the wavefronts to reorient and the ray changes direction. If the second medium is slower, the refracted path angles more toward the normal; if it’s faster, it bends away from the normal. Reflection, by contrast, is when part of the wave bounces back toward the source, not when it changes direction forward through the boundary. Spatial and temporal describe dimensions or time, not the bending at a boundary.

Refraction is the bending of a sound wave as it crosses into a different medium because the wave travels at a different speed in each medium. In ultrasound, tissue interfaces have different speeds of sound (soft tissue around 1540 m/s, bone much faster), so when the wave hits the boundary at an angle, the change in speed causes the wavefronts to reorient and the ray changes direction. If the second medium is slower, the refracted path angles more toward the normal; if it’s faster, it bends away from the normal. Reflection, by contrast, is when part of the wave bounces back toward the source, not when it changes direction forward through the boundary. Spatial and temporal describe dimensions or time, not the bending at a boundary.