# P1 Topic 4: Waves and Earth

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• Created by: nicola
• Created on: 15-04-15 11:08
What is the frequency of the human hearing?
Sound waves between 20Hz and 20,000Hz
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What is the frequency of Ultrasound?
Sound waves above 20,000Hz (above the frequency of human can hear)
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what is the frequency of infra sound?
Sound waves below 20Hz (below the frequency of human cans hear)
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What are the uses of ultrasound?
Communication between animals and solar and foetal scanning.
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How can you use ultrasound for sonar and foetal scanning?
The distance to an object or bounary can be calculated by timing how long the sound wave takes to travel there and echo back. computers use this information to produce an image (remember the distance the wave travels is twice the distance the object.
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What are the uses of infra sound?
Communication between animals and the detection of animal movement, volcanic eruption and meteor strikes
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What are seismic waves?
waves caused by earthquakes or large explosion
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What are P-waves?
They are faster than S-waves, arrive before S-waves, Longitudinal and can travel through solids and liquids(e.g. crust, mantle, outer and inner core)
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What are S-waves?
They are slower they P-waves, arrive second after P-waves are transverse waves and can onl
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What are the four layers of the earth?
Crust, mantle, outer core and inner core.
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What are the properties of the crust?
solid-very thin-made up of tectonic plates-P and S waves can both travel thought the crust.
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What are the properties of the mantle?
Solid characteristics (flows very slow)-half the depth of the earth-density increases towards the center-so P and S waves are refracted (bent) as they speed up.
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What are the properties of the outer core?
Liquid-less dense than mantle-density increases towards the center-so P waves are refracted (bent) as they speed up.
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What are the properties of the inner core?
Solid-very dense- so P-waves travel faster here
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What is the Mantel/outer boundary and what are the properties?
S-waves reflected, P-waves suddenly slow so refract sharply
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What are convection currents?
The mantle near the core is heated and becomes less dense so rises. the mantle near the crust cool and becomes more dense so falls. this cycle causes a current that move the tectonic plates.
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What is Tsunami?
A huge wave caused by a earthquake under the sea.
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What is an Earthquake?
When tectonic plates are constantly moving due to convection currents in the mantle. pressure builds up due to friction between the tectonic plates, when the plates suddenly move relative to each other Earthquakes are produced.
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How could you predict an Earthquakes?
It is very different to predict earthquakes - force and friction between plates is difficult to measure and previous earthquakes only give and idea how likely they are to happen in the future.
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How do scientist try and locate Earthquakes?
Triangulation - the distance from the epicenter of an Earthquake to a seismometer can be calculated from the time difference between the P and S waves arriving. Distances from three different seismometer can be used to pinpoint the epicenter.
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How does Triangulation work?
Draw circles on map around each seismometer with the correct radius to see where they all cross.
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## Other cards in this set

### Card 2

#### Front

What is the frequency of Ultrasound?

#### Back

Sound waves above 20,000Hz (above the frequency of human can hear)

### Card 3

#### Front

what is the frequency of infra sound?

### Card 4

#### Front

What are the uses of ultrasound?

### Card 5

#### Front

How can you use ultrasound for sonar and foetal scanning?