An ultrasound transducer is used to image internal structures in a patient's body.
In ophthalmic ultrasound scans, a coupling gel is applied directly to the patient's eyelid or eye surface before placing the transducer probe. Explain why the scan would fail to produce a clear image of internal structures if this coupling gel were omitted.
A beam of ultrasound is directed through a layer of subcutaneous fat into the underlying femur bone. Calculate the percentage of the incident ultrasound intensity that is transmitted across the fat–bone boundary.
acoustic impedance of bone = 6.8×106 kg m−2 s−16.8 \times 10^6 \text{ kg m}^{-2} \text{ s}^{-1}6.8×106 kg m−2 s−1 density of subcutaneous fat = 920 kg m−3920 \text{ kg m}^{-3}920 kg m−3 speed of ultrasound in fat = 1450 m s−11450 \text{ m s}^{-1}1450 m s−1
12 exam-style questions on AQA A Level Physics Non-ionising imaging (A-level only), covering Ultrasound imaging (A-level only), Fibre optics and endoscopy (A-level only), and Magnetic resonance (MR) scanner (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.