(a(i))[2]
State the meaning of the specific acoustic impedance of a medium.
(a(ii))[2]
The intensity reflection coefficient $\alpha$ is defined by $\alpha = \dfrac{(Z_2 - Z_1)^2}{(Z_2 + Z_1)^2}$. Explain what the symbols in this expression mean. $\alpha$: and $Z_2$ and $Z_1$.
(b)
A parallel beam of ultrasound enters a muscle with intensity $I_0$. It travels through $3.4\,\text{cm}$ of muscle before reaching the boundary with a bone, as shown in Fig. 4.1. The ultrasound intensity as it enters the bone is $I_T$.