Describe the process by which the piezoelectric crystal in a transducer produces ultrasound waves for medical diagnosis.
A parallel ultrasound beam is incident at the boundary between two media, as shown in Fig. 10.1. The media have specific acoustic impedances $Z_1$ and $Z_2$. At the boundary, a fraction $\alpha$ of the incident intensity of the ultrasound beam is reflected. State what is meant by specific acoustic impedance.
Describe how $\alpha$ varies with the relative magnitudes of $Z_1$ and $Z_2$.
A parallel ultrasound beam of intensity $I_0$ enters a region of soft tissue. After travelling a distance of $2.1\,\text{cm}$ through this tissue, the intensity of the ultrasound is $0.62 I_0$. Calculate the linear attenuation coefficient $\mu$ of ultrasound in the soft tissue. Give a unit with your answer.