A LevelPhysicsOCRExam Questions6. Particles & Medical PhysicsUltrasound

Ultrasound (OCR A Level Physics): Exam Questions

Exam code: H556

23 mins6 questions

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Ultrasound

1a
2 marks

This question is about the medical use of ultrasound.

a)

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

[2]

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1b
2 marks

b)

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.

[3]

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2a
2 marks

a)

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

[2]

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2b
3 marks

b)

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

[3]

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3a
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2 marks

The density of a sample of bone is 1.9 text  g cm end text to the power of negative 3 end exponent. The speed of ultrasound in the bone is 4.08 text  km s end text to the power of negative 1 end exponent.

Calculate the acoustic impedance Z of bone.

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3b
3 marks

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

The acoustic impedance of muscle is 1.7 \times 10^6 \text{ kg m}^{-2} \text{ s}^{-1}.

Calculate the intensity reflection coefficient for this boundary.

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3c
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.

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