Ultrasound (OCR A Level Physics): Exam Questions

Exam code: H556

22 mins6 questions
1a
2 marks

This question is about the medical use of ultrasound.

In ultrasound scanning, explain what is meant by impedance (acoustic) matching and how it may be achieved.

1b
2 marks

There are several different types of ultrasound scanning techniques.

Explain how an A-scan could be used to measure the thickness of a patient’s eye lens. You may draw a diagram to help with your answer.

2a
2 marks

Explain how an ultrasound transducer can emit ultrasound. You do not need to describe the design of the transducer.

2b
3 marks

Explain how the reflection of ultrasound at a boundary between two tissues depends on the physical properties of the tissues.

[3]

1a
2 marks

The density of a sample of bone is 1.9 g cm−3. The speed of ultrasound in the bone is 4.08 km s−1.

Calculate the acoustic impedance Z of bone.

Z = .................................................. kg m−2 s−1

1b
2 marks

An ultrasound pulse is incident at the boundary between muscle and bone.

The acoustic impedance of muscle is 1.7×106 kg m−2 s−1.

Use your answer to (a) to calculate the intensity reflection coefficient for this boundary.

intensity reflection coefficient = ..................................................

1c
6 marks

Describe the principles of an ultrasound B-scan and how it differs from an A-scan.

Your answer should include:

  • how the ultrasound is produced

  • the role of the coupling gel

  • how the 2D image is built up