If a 5-MHz wave travels through 5 cm of soft tissue, what happens to the propagation speed if a 3.5-MHz transducer is selected instead?

• A. Increases
• B. Decreases
• C. No change
• D. Not enough information given

Answer: (C)

The speed of sound in a medium, such as soft tissue, is primarily determined by the properties of that medium (e.g., its density and elasticity) rather than by the frequency of the wave itself. Regardless of whether a 5-MHz or a 3.5-MHz transducer is used, the wave will propagate at the same speed in soft tissue.

In soft tissue, the speed of sound is generally around 1540 meters per second. This speed remains constant as long as the medium does not change. Therefore, no matter which frequency transducer is selected, the propagation speed will not vary as it is a characteristic of the medium itself.

This concept highlights the distinction between wave frequency and speed: while frequency can affect the wavelength and the energy of the wave, it does not influence how quickly the wave travels through a given material.