Sound too high to hear
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Transcript of Sound too high to hear
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Sound too high to hearUltrasoundUltrasoundSlide 1
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Slide 2
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Sailors can use ultrasound to find the depth of the sea using an echo-sounder or S.O.N.A.R. The sound used by the sonar is too high for us to hear. It is called ultrasound. (Sound waves above 18,000 Hz) Slide 3
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Dolphins make highpitched squeaks and listen to the echoes. Bats also use ultrasonicsounds, to echo-locatetheir flying food (moth). Slide 4
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Cleaning things with ultrasoundSlide 5
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Slide 6Ultrasound scanners have advantages over X rays:* X rays are ionising and can damage cells
* Ultrasound is reflected at boundaries between different types of tissue so they can be used to scan organsTo obtain an echo at a boundary:tissue densities must be different.
(The acoustic impedance of the two tissues must be different = product of speed x density)
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Detecting faults inside metal objects Slide 7
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Whales sing messages to each other over hundreds of miles.Their sex life is being disturbed by noisy ships.
Sound travels further and faster in water than in air because...
Slide 8
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Geologists use echo-sounding to search for oil and gasQ1. Which microphone will receive the sound first?Q2. How deep is the hard rock layer?Slide 9
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Most students should be able to: Compare ultrasound to audible sound waves. Describe a range of uses of ultrasound, including cleaning and detecting cracks.
Some students should also be able to: Explain how ultrasound can be used for medical scanning and the advantages of ultrasound over X-ray techniques. Work out the distance between interfaces from diagrams of oscilloscope traces.
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1a. Organs have boundaries with different tissue densities
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1a. Organs have boundaries with different tissue densities 1b. No ionising radiation is used
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12
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28.3 squares = 100mm
So 1 square =1
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1Flaw 1 = 2.8 sqs
= mm
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1Flaw 1 = 2.8 sqs 2.8 x 12 mm = 33.6mm
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1Flaw 2 = sqs
= mm
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1Flaw 2 = 4.1 sqs
= mm
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28.3 squares = 100mm
So 1 square = 100 8.3 = 12mm1Flaw 2 = 4.1 sqs 4.1 x 12 mm = 49.2mm
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