Refraction in ultrasound occurs when:

Refraction in ultrasound occurs when:

• A. The wave changes direction as it passes an interface with density differences
• B. The wave is completely reflected
• C. The wave is absorbed without a trace
• D. The wave speeds up but keeps direction

Answer: (A)

Refraction happens when an ultrasound wave crosses from one tissue into another with a different propagation speed. Because the second medium changes the speed of the wave, the portion of the wavefront that enters the new medium travels at a different rate than the portion still in the first, causing the beam to bend. This bending follows Snell’s law and only occurs when the incidence isn’t perpendicular to the boundary and there’s a speed (and impedance) difference between the media. If the wave is completely reflected, that’s reflection, not refraction; if it’s absorbed, that’s attenuation; and if the speed changes but the direction stays the same, that isn’t refraction.

Refraction happens when an ultrasound wave crosses from one tissue into another with a different propagation speed. Because the second medium changes the speed of the wave, the portion of the wavefront that enters the new medium travels at a different rate than the portion still in the first, causing the beam to bend. This bending follows Snell’s law and only occurs when the incidence isn’t perpendicular to the boundary and there’s a speed (and impedance) difference between the media. If the wave is completely reflected, that’s reflection, not refraction; if it’s absorbed, that’s attenuation; and if the speed changes but the direction stays the same, that isn’t refraction.