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GCSE Questions - Waves

Q10. Ultrasound has industrial applications as well as medical applications.
One industrial application of ultrasound is testing an aeroplane wing to make sure that
there are no cracks.

(a) State the minimum frequency of an ultrasound wave. Include the correct unit.

20,000 Hz

[1 mark]

(b) An ultrasound pulse is transmitted from the top of a wing as shown in the diagram.

There is a small crack in the wing. The ultrasound can be used to detect how far the crack is from the surface of the wing.

(i) The ultrasound signal on its own does not directly give the distance to the crack. What measurement is taken to determine the distance to the crack?

The time taken for the pulse to travel from the transmitter to the crack and back to the receiver.

[1 mark]

(ii) What other information is needed to calculate the distance from the surface of the wing to the crack?

The speed of ultrasound when travelling within the wing.

[1 mark]

(iii) Describe what happens to the ultrasound pulse when it reaches the small crack.

It is partially reflected and partially transmitted

[2 marks]

(c) An aircraft is safe to fly for at least 2000 hours after a crack begins to develop in a wing. The wing is tested after every 500 hours of flying time. If a crack is found the wing is replaced immediately. If there is a crack in the wing, an ultrasound test will detect the crack 99% of the time.

Suggest why the interval between tests is less than the safe flying time after a crack develops.

If a fault is missed on an inspection it will still be safe until the next inspection is due.

[1 mark]

(Total 6 marks)