Physics 9702 · AS & A Level · Production and use of ultrasound
Production and use of ultrasound — practice question
Table 8.1 presents some data about the properties of air, gel and body tissue. The data are given to three significant figures.
(a(i))[1]
Demonstrate that the specific acoustic impedance of gel is $1.68 \times 10^{6}\,\text{kg m}^{-2}\,\text{s}^{-1}$.
(a(ii))[2]
Complete Table 8.1 by finding the missing values to three significant figures. Use the space below for any working you need.
(b(i))[2]
Using the information in (a), calculate the intensity reflection coefficient for an air-tissue boundary.
(b(ii))[1]
Using the information in (a), calculate the intensity reflection coefficient for a gel-tissue boundary.
(c)[2]
Use your answers in (b) to explain why gel is placed on the skin during ultrasound scanning.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “specific acoustic impedance can be written as $Z = 1200\times1400 = 1.68\times10^6\,\mathrm{kg\,m^{-2}\,s^{-1}}$” …