Lateral resolution decreases when the distance between vectors (lines of sight) is greater than the beam width. Which choice describes this condition?

• A. A When the frequency is doubled
• B. B When the transducer is moved from tissue to air
• C. C When the distance between vectors is greater than the beam width
• D. D When the beam is perfectly focused

Answer: (C)

Lateral resolution depends on how wide the beam is as it travels sideways. If the two lines of sight to targets are separated by more than the beam’s width, those targets don’t lie within the same beam footprint, so the system’s ability to distinguish them side-by-side worsens. This spacing condition—when the distance between vectors is greater than the beam width—describes why lateral resolution would decrease. Other factors like increasing frequency narrow the beam (often improving lateral resolution), moving the transducer away from tissue (which disrupts coupling and image quality), or perfectly focusing the beam (which would enhance, not degrade, resolution) don’t capture this spacing-related limit.