# P4 - Ultrasound

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What is ultrasound?
Sound above 20 000 Hz which is a higher frequency than humans can hear
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What does it travel as?
A pressure wave containing compressions and rarefactions
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What are compressions?
regions of high pressure
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What are rarefactions?
regions of lower pressure
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What are the features of longitudinal sound waves?
They can't travel through a vacuum (the denser the medium, the faster a sound wave travels). The higher the frequency, the smaller the wavelength. The louder the sound, the more energy that is carried by the wave and the larger its amplitude
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In a longitudinal wave, what are the vibrations?
Parallel to the direction of the wave
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In a transverse wave, what are the vibrations?
At right angles to the direction of the wave
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What happens during the process of using ultrasound to break down kidney stones?
A high-powered ultrasound beam is directed at the kidney stones, he ultrasound energy breaks the stones down into smaller pieces, the tiny pieces re then excreted from the body
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What happens during the process of using ultrasound in a body scan?
A pulse of ultrasound is sent into the body, at each boundry between tissues some ultrasound is reflected and the rest is transmitted, the returning echoes are recorded and used to build up an image of the internal structure
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Why can ultrasound be used in a body scan?
When ultrasound is reflected from different interfaces in the body, the depth of each structure is calculated by using the formula, distance = speed x time, knowing the speed of ultrasound for different tissue types and the time for an echo to return
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Why is ultrasound preferred to x-rays?
it is able to produce images of soft tissue, it doesn't damage living cells
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## Other cards in this set

### Card 2

#### Front

What does it travel as?

#### Back

A pressure wave containing compressions and rarefactions

### Card 3

#### Front

What are compressions?

### Card 4

#### Front

What are rarefactions?

### Card 5

#### Front

What are the features of longitudinal sound waves?