P1 Unit 4: Waves and the Earth

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  • Created by: nicola
  • Created on: 18-04-15 09:49
What is sound?
Sound waves between 20Hz and 20,000Hz (the range of which humans hear).
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What is Ultrasound?
Sound waves above 20,000Hz (above the frequency we can hear).
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What is Infrasound?
Sound waves below 20Hz (below the frequency we can hear).
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What are the uses of ultrasound?
Communication between animals, sonar and foetal scanning.
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How can Ultrasound been used for Sonar and foetal sanning?
The distances to an object or boundary can be calculated by timing how long the sound waves takes to travel there and echo back. Computers use this information to produce an image (distance the wave travels is twice the distance the object is away).
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What are the uses of Infrasound?
Communication between animals and the detection of animals movement, volcanic eruptions and metor srikes.
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What are seismic waves?
Waves caused by earthquakes or a large explosions.
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What are P-waves and there properties?
P-wave stand for Primary waves. P-waves are faster than secondary waves, Arrive before secondary wave, are longitidial and can travel through solids and liquids (i.e. Crust, Mantle, Outer and Inner Core).
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What are S-waves and there properties?
S-waves stand for Secondary waves. S-waves are slower than P-waves, arrice second after pirmary waves, are transverse waves and can only travel through solids (i.e. Crust and matle)
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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, both P-waves and S-waves can travel through the crust.
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What are the properties of the Mantle?
Solid characteristics (flow very slow), half the dept of the Earth's density increases towards the centre - so P-waves and S-waves are refracted (bent) as they speed up.
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What are the properties of mantle/outer core boundary?
S-waves are reflected, P-waves seddenly slow so refract sharply.
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What are the properties of outer core?
Liquid, less dense than mantle, desnsity increases towards the centre, so P-waves are refracted (bent) as they speed up.
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What are the propeties of the inner core?
Solid, very dense, P-waves travel faster here.
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What is convestion current?
The mantle near the core is heated and becomes less dense so rises. The mantle near the crust cool and becomes less desnse so rises. This cycle causes a current that move the techonic plates.
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What is an tsunami?
A huge waves caused by an Eathquake under the sea.
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What is an Earthquakes?
Tectonic plates are constanly moving due to convection currents in the mantle. Pressure builds up due to friction between the tectonic plates, when the plates suddenly more relative to each other Earthquakes are produced.
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How are Earth predicted?
It is very difficult to preidct earthquakes-the force and friction between plates is difficult to measure and previous earthquakes only give an idea how likely they are to happen in the future.
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How are Eathquakes located? 1/2
Trigangulation - the distance from the epicentre of an earthquake to a seismometr can be calculated from the time difference between the P and S waves arriving.
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How are Earthquakes located? 2/2
Distances from three different seisometers can be used to pinpoint the epicentre by triangulation (draw circles on a map around each seimometer with correct radius to see where they all cross.
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Other cards in this set

Card 2

Front

What is Ultrasound?

Back

Sound waves above 20,000Hz (above the frequency we can hear).

Card 3

Front

What is Infrasound?

Back

Preview of the front of card 3

Card 4

Front

What are the uses of ultrasound?

Back

Preview of the front of card 4

Card 5

Front

How can Ultrasound been used for Sonar and foetal sanning?

Back

Preview of the front of card 5
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