What benefit would you obtain by choosing a transducer having a large diameter compared to one having a small diameter?

• A. It can focus at greater depths
• B. Increases the frequency
• C. Increases the beam diameter in the far field
• D. A and C

Answer: (A)

A larger diameter transducer provides a bigger aperture, which reduces beam divergence and allows the beam to stay narrow farther from the source. This means you can place the focal region deeper in tissue and still maintain good lateral resolution, effectively enabling focusing at greater depths. Frequency, on the other hand, is set by the piezoelectric material and the element thickness, not by the diameter. The beam won’t naturally widen at the far field just because the diameter is larger; in fact, a larger aperture tends to produce a narrower beam in the far field, improving focus rather than increasing beam width.