When the system is imaging more deeply, the time from one pulse to the next is ______.

When the system is imaging more deeply, the time from one pulse to the next is ______.

• A. Shorter
• B. Same
• C. Random
• D. Longer

Answer: (D)

When you image deeper, the pulse has to travel farther down and back before you can send the next pulse. The system must wait for those echoes to return, so the interval between transmissions—the pulse repetition interval—gets longer as depth increases. If you fired again too soon, echoes from the previous pulse would overlap with the new one, creating ambiguity about where echoes came from. So the time from one pulse to the next is longer, and the pulse repetition frequency decreases with depth.

When you image deeper, the pulse has to travel farther down and back before you can send the next pulse. The system must wait for those echoes to return, so the interval between transmissions—the pulse repetition interval—gets longer as depth increases. If you fired again too soon, echoes from the previous pulse would overlap with the new one, creating ambiguity about where echoes came from. So the time from one pulse to the next is longer, and the pulse repetition frequency decreases with depth.