(a(i))[2]
Explain why ultrasound used for medical diagnosis is sent out in pulses.
(a(ii))[3]
Explain the principles behind detecting ultrasound waves used in medical diagnosis.
(b(i))[1]
The specific acoustic impedances of two media are $Z_1$ and $Z_2$. The intensity reflection coefficient $\alpha$ for the boundary between these two media is defined by: $\alpha = \dfrac{(Z_1 - Z_2)^2}{(Z_1 + Z_2)^2}$. Calculate, to three significant figures, the fraction of ultrasound intensity reflected at the boundary between air and soft tissue.
(b(ii))[2]
Use your result from (b)(i) to explain why gel is placed on the skin surface during an ultrasound scan.