A research team in Singapore uses ultrasound to detect cracks inside metal pipes. The ultrasound wave reflects when it meets a crack. Which property of waves allows this detection method to work?

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Question

A research team in Singapore uses ultrasound to detect cracks inside metal pipes. The ultrasound wave reflects when it meets a crack. Which property of waves allows this detection method to work?

Accepted Answer

Ultrasound waves are reflected at boundaries between different media. — Award 1 mark for identifying that reflection at boundaries is the key property. A is incorrect — refraction would not cause the wave to return to the detector. C is incorrect — while true, this describes wave speed, not the detection mechanism. D is incorrect — the frequency defines ultrasound but does not explain how cracks are detected.

Answer

Ultrasound waves are reflected at boundaries between different media.

Answer

Ultrasound waves have a frequency above 20 000 Hz.

Answer

Ultrasound waves travel faster in solids than in liquids.

Answer

Ultrasound waves can be refracted at boundaries.

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