Speed is determined by the density and stiffness of the medium. Which properties determine the speed of ultrasound?

Speed is determined by the density and stiffness of the medium. Which properties determine the speed of ultrasound?

• A. Density and Stiffness
• B. Temperature and Viscosity
• C. Frequency and Amplitude
• D. Attenuation and Reflection

Answer: (A)

The main idea is that how fast ultrasound travels through a medium depends on the medium’s density and how stiff it is. A stiffer material resists compression more, so the wave can move through it more quickly. At the same time, a denser material has more inertia to move, which slows the wave down. Together, these properties set the wave’s speed, often summarized by v ~ sqrt(stiffness/density). So the best choice points to density and stiffness because they directly govern how quickly a compressional wave propagates. Temperature and viscosity influence the medium in other ways and aren’t the primary determinants of ultrasound speed. Frequency and amplitude describe the wave itself, not the medium’s transmission speed, and attenuation and reflection are effects that occur as the wave interacts with the medium rather than factors setting the speed.

The main idea is that how fast ultrasound travels through a medium depends on the medium’s density and how stiff it is. A stiffer material resists compression more, so the wave can move through it more quickly. At the same time, a denser material has more inertia to move, which slows the wave down. Together, these properties set the wave’s speed, often summarized by v ~ sqrt(stiffness/density).

So the best choice points to density and stiffness because they directly govern how quickly a compressional wave propagates. Temperature and viscosity influence the medium in other ways and aren’t the primary determinants of ultrasound speed. Frequency and amplitude describe the wave itself, not the medium’s transmission speed, and attenuation and reflection are effects that occur as the wave interacts with the medium rather than factors setting the speed.