Axial resolution is affected by focusing.

• A. Depends on frequency
• B. Not enough information
• C. True
• D. False

Answer: (D)

Axial resolution is governed by the spatial pulse length, which is how long the sound pulse is along the direction of travel. This length depends on the number of cycles in the emitted pulse and the wavelength (which in turn depends on frequency). Shorter pulse length—achieved by using higher frequency or fewer cycles—improves axial resolution.

Focusing shapes the beam laterally, narrowing the beam width at the focal point to improve lateral resolution, but it does not change the length of the pulse along the axis. Because axial resolution depends on the pulse length, while focusing changes the beam’s cross-sectional width, focusing does not affect axial resolution. So the statement is false. Use higher frequency or fewer cycles to improve axial resolution; focusing helps laterally, not along the axis.