MYP Physics · 19 · data analysis
Find depth from an ultrasound echo
Physics in society · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- routine
- Marks
- 6
- Topics
- 1
- Answer
- Complete
An ultrasound pulse travels through soft tissue at 1540 m s⁻¹. The strongest echo returns 80 μs after the pulse is sent.
- a
Explain Explain why the distance to the boundary is half the total pulse travel distance.
2 marks - b
Calculate Calculate the depth of the reflecting boundary.
3 marks - c
State State one reason the real depth may differ from this result.
1 mark
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a
Explain Explain why the distance to the boundary is half the total pulse travel distance.
Read the data before explaining it. Quote the relevant values or trend, show the comparison or calculation, and then connect that numerical evidence to the physical conclusion—including uncertainty or anomalies when they matter.
- 1
States that the pulse travels from the probe to the boundary.
- 2
States that the echo then returns from the boundary to the probe, so the recorded time is for a round trip.
b
Calculate Calculate the depth of the reflecting boundary.
Read the data before explaining it. Quote the relevant values or trend, show the comparison or calculation, and then connect that numerical evidence to the physical conclusion—including uncertainty or anomalies when they matter.
- 1
Converts 80 μs to 80 × 10⁻⁶ s.
- 2
Uses depth = vt ÷ 2.
- 3
Obtains 1540 × 80 × 10⁻⁶ ÷ 2 = 0.0616 m, or 6.16 cm.
c
State State one reason the real depth may differ from this result.
Read the data before explaining it. Quote the relevant values or trend, show the comparison or calculation, and then connect that numerical evidence to the physical conclusion—including uncertainty or anomalies when they matter.
- 1
States a valid limitation such as wave speed varying between tissues, uncertain echo origin, probe angle, timing resolution, or layered propagation.
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