P12

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What are mechanical waves?
Vibrations that travel through a medium
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What are electromagentic waves?
All travel through a vacuum at same speed, no medium needed
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What happens to the oscillations of a transverse wave?
They are perpendicular to the direction of energy transfer
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What are all electromagnetic waves?
Transverse waves
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What happens to the oscillations in longitudinal waves?
They are parallel to direction of energy transfer
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What wave type are sound waves?
Longitudinal
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What type of waves are mechanical waves?
Longitudinal + transverse
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What is the amplitude of a wave?
The maximum displacement of a point on the wave from undisturbed position *
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What is the link between amplitude and energy?
The bigger the amplitude the more energy carried
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What is the wavelength of a wave?
The distance from a point on the wave to equiv point on adjacent wave*
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What is the frequency of a wave?
The number of waves passing through a point*
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What is the speed of a wave?
The distance travelled by each wave every second through a medium
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How to measure the speed of sound in air?
Two people, opposite ends one bangs cymbal and time interval between seeing and hearing
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How to measure reflection of waves?
Ruler in ripple tank, see if angles are same
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What is refraction?
Waves change direction in which they are travelling as they cross a boundary between one medium + another
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What happens when plane waves cross a boundary at a non zero angle to boundary?
Each wave-front changes speed + direction
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What is the difference between refracted waves + incident rays?
Same freq, diff speed + wavelength
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What feature of the wave depends on what happens during reflection?
The wavelength on wave and surface
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What happens if a substance absorbs waves?
Temp increases
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What happens as waves travel through a substance?
Amplitude gradually decreases because some energy absorbed
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What does any object vibrating in air do?
Makes layers of air near object vibrate, makes layers of air next to them vibrate, vibrating object pushed + pulls on air, sending out vibrations
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How can the speed of sound increase in air?
Increasing temp
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What can sound waves not travel through and how to test this?
Vacuum and electric bell test
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What Freq can our ears detect?
20Hz - 20,000 Hz
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How do our ears work?
Sound waves vibrate our ear drum which sends signals to brain
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What are sound waves entering a solid converted to?
Vibrations
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Why is freq range of ear limited?
Because conversion of this only works over limited freq range
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What does echo sounding use?
Pulses of high freq sound waves to detect objects deep in water
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What is an echo?
The reflection of sound waves from a smooth surface
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What are ultrasound waves?
Sound waves above the highest freq that humans can hear
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What are ultrasound scans used for?
Baby scans, image of organs
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What is an ultrasound scanner made up of?
An electronic device called a transducer placed on body and a display screen
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What does the transducer do?
Produces and detects ultra sound waves
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What are the advantages of using ultrasound waves?
Reflected at boundaries between diff types of tissues used for tissues and organs + non ionising
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How can ultrasound waves be used in industry?
Detect flaws and cracks in metal casting
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Where do earthquakes occur from?
Focus
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What is the point on the earths surface called?
Epicentre
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What are earthquakes detected by?
Seisomometers
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What are primary waves?
Initial tremors, longitudinal, push + pull material, from inside
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What are secondary waves?
Cause more tremors later, transverse, slower than P waves, shake material, only in earth's crust
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What are L waves?
Arrive last, violent movements up+ down, slower than both waves, only in crust
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What do P and S waves do when travelling through mantle?
Bend
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Why do they bend?
Due to speed changing with depth, so direction changes too
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What do P waves do at the boundary between mantle + outer core?
Refract because speed changes abruptly
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Why cant' S waves travel through liquid outer core?
They are transverse
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What is the shadow zone?
Zone of 105-142 where no waves recorded
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What does the shadow zone show?
P waves are refracted at boundary, because second refraction is further around the waves cant reach zone
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Other cards in this set

Card 2

Front

What are electromagentic waves?

Back

All travel through a vacuum at same speed, no medium needed

Card 3

Front

What happens to the oscillations of a transverse wave?

Back

Preview of the front of card 3

Card 4

Front

What are all electromagnetic waves?

Back

Preview of the front of card 4

Card 5

Front

What happens to the oscillations in longitudinal waves?

Back

Preview of the front of card 5
View more cards

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