Reflection, transmission and pulse-echo techniques Quiz
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5 questions, one answer each
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1. A pulse of ultrasound returns after 0.020 s. The speed is 1500 m s⁻¹. How far away is the boundary?
- A. 30 m
- B. 15 m
- C. 60 m
- D. 3.0 × 10⁴ m
2. What happens when a wave reaches an interface?
- A. All of it is reflected
- B. All of it is transmitted
- C. Part is reflected and part is transmitted
- D. Its frequency doubles
3. Why does a higher-frequency ultrasound resolve smaller detail?
- A. Its wavelength is shorter
- B. Its speed is greater
- C. Its pulses are longer
- D. It is absorbed less
4. Two echoes arrive 2.0 μs apart. What must the pulse duration be to see them as separate?
- A. More than 2.0 μs
- B. Exactly 4.0 μs
- C. It makes no difference
- D. Less than 2.0 μs
5. Why is gel put between an ultrasound probe and skin?
- A. To raise the frequency of the pulse
- B. To cool the skin
- C. To remove air so less ultrasound is reflected at the skin
- D. To lengthen the pulse