When a reflector is located deep the time from pulse creation to reception is ______.

When a reflector is located deep the time from pulse creation to reception is ______.

• A. Longer
• B. Shorter
• C. Directly related
• D. Inversely related

Answer: (A)

When the reflector is deeper, the ultrasound wave has to travel a longer distance to reach it and then return. With the speed of sound in tissue roughly constant, more distance means more travel time. The round-trip time can be described by t = 2 × depth / speed, so as depth increases, the time from pulse creation to reception increases. That’s why the correct description is that the time is longer for deeper reflectors. Shorter would imply less travel, which isn’t the case, and inversely related would imply time decreases with depth, which is incorrect. Being deeper also means the time is directly related to depth, but the specific, precise description is that it’s longer.

When the reflector is deeper, the ultrasound wave has to travel a longer distance to reach it and then return. With the speed of sound in tissue roughly constant, more distance means more travel time. The round-trip time can be described by t = 2 × depth / speed, so as depth increases, the time from pulse creation to reception increases. That’s why the correct description is that the time is longer for deeper reflectors. Shorter would imply less travel, which isn’t the case, and inversely related would imply time decreases with depth, which is incorrect. Being deeper also means the time is directly related to depth, but the specific, precise description is that it’s longer.