Waves at interfaces and pulse-echo Quiz
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5 questions, one answer each
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1. Ultrasound pulses return 40 μs after transmission. If v = 1540 m s⁻¹, what is the depth of the boundary?
- A. 6.2 cm
- B. 12 cm
- C. 1.2 cm
- D. 3.1 cm
2. What is the main reason for using a coupling gel?
- A. It lowers the frequency
- B. It removes the air gap that would reflect the ultrasound
- C. It amplifies the echo electronically
- D. It makes the pulse shorter
3. Which change improves the resolution of detail in the image?
- A. Lower frequency
- B. Longer wavelength
- C. Higher frequency
- D. Longer pulses
4. A pulse has a duration of 0.50 μs in tissue where v = 1500 m s⁻¹. What is the pulse length?
- A. 7.5 × 10⁻⁴ m
- B. 3.0 × 10⁹ m
- C. 7.5 × 10⁻⁷ m
- D. 3.3 × 10⁻⁹ m
5. Which statement about the frequency of an ultrasound pulse crossing into a second medium is correct?
- A. It is multiplied by the ratio of the speeds
- B. It is halved
- C. It becomes equal to the frequency of the echo from the deeper layer
- D. It is unchanged, while the wavelength changes