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Edexcel GCSE Physics > SP4 - Waves ✓ > Flashcards

SP4 - Waves ✓ Flashcards

1
Q

SP4a - Describe a transverse wave, giving examples.

A
  • Paritcles vibrate perpendicular to their direction of travel.
  • They transfer energy
  • They all travel at the same speed in a vacuum (3x108)
  • All EM waves are examples of this
  • Water waves are transverse
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2
Q

SP4a - Describe a longitudinal wave, giving examples.

A
  • Particles vibrate parallel to direction of travel
  • Areas of compression and rarefraction
  • Sound waves
  • Seismic P waves
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3
Q

SP4a - Descirbe the following features of a transverse wave:

  1. Frequency
  2. Period
  3. Wavelength
  4. Amplitude
A
  1. The amount of waves passing in a second (measured in Hertz Hz. Determines pitch or colour)
  2. The time it takes one wave to pass a point
  3. The length in m from one point to the next identical point of a wave
  4. The distance in m from a waves rest position to its trough or peak
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4
Q

SP4b - What are the two formulas for wave speed?

A

v = d/t

(Velocity = distance ÷ time)

v = f x λ

(Velocity = frequncy x wavelength)

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5
Q

SP4b - Using two buoys, how can you measure the speed of waves?

A
  • Measure the distance the buoys are apart.
  • Record the amount of time it takes for a single wave to get from one to the other.
  • Do distance/time to get the wave speed.
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6
Q

SP4b CP - How can you use a wave tank to investigate the speed of waves?

A
  • Set up a wave tank filled with water and a straight dipper with a ruler along the side
  • Vary the voltage provided to the straight dipper till there are at least 2 waves visible at any point
  • Count how many waves form in 10 seconds and divide by 10 to get your frequency
  • Using the ruler estimate the wavelength of a wave
  • Frequency x wavelength
  • Alternatively, record how long it takes the wave formed to travel a certain distance and to distance/time
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7
Q

SP4b CP - How can you use a metal rod to investigate the speed of waves in solids?

A
  • Suspend a metal rod using clamp stands
  • Hold a smartphone with a frequency app at one end
  • Hit the other end of the rod with a hammer and record the peak frequency
  • Meausure the length of the rod
  • Frequency x wavelength
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8
Q

SP4c - How does refraction occur?

A
  • When a ray of light reaches an interface (boundary) between substances, it changes speed (because light’s speed is dependant on the density of the substance it travels in).
  • If it slows down it bends towards the normal and if it speeds up it bends away
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9
Q

SP4c - Using water waves as a model, explain why refraction occurs.

A
  • Waves of water travel faster is depper water than shallow water
  • They also are longitudinal so can be represented with lots of parallel lines rather than one line
  • When the wave of water reaches a boundary between shallow and deep, the part of each line that is furthest ahead, will reach the boundary first and slow down first.
  • This gradual change in which parts slow down means that the wave bends towards the normal
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10
Q

SP4d - What are the definitions of the following:

  • Reflect
  • Refract
  • Transmit
  • Absorb
A
  • Reflect: The waves bounce off
  • Refract: The wave passes into the new material but changes direction
  • Transmit: The wave passes through without being absorbed or reflected
  • Absorbed: The wave disappears as the enrgy it was carrying is transferred into the material
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11
Q

SP4d - Why is a prism able to split white light into a spectrum?

A

Each frequency of light changes speed at a slightly different rate meaning that at the right angles they can be split up

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12
Q

SP4e - Describe the process of a sound being heard by and ear. [6 marks]

A
  • Sound waves enter the ar canal which focuses it
  • The eardum is a thin membrance which vibrates due to the soundwaves’ vibrations
  • Vibrations are passed on to tiny bones which amplify the vibrations
  • Vibrations are passed on to the liquid inside the cochlea
  • Tiny hairs inside the cochlea detect these vibrations and convert them to electrical impulses
  • Impulses travel along the auditory nerve to reach the brain
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13
Q

SP4e - How does the cochlea work?

A
  • The cochlea has a membrane covered with hair cells
  • Each hair cell is connected to a neurone so that when it detects a vibration of its frequency it creates and electrical signal
  • The cochlea is a spiral with the outmost part (the base) detecting hgih frequencies (up to 20000Hz) and the low end (the apex) detecting lower frequencies (down to 20Hz)
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14
Q

SP4e - Explain why as people get older, their range of hearing may decrease.

A
  • As people get older, the hairs of the base and apex of their cochlea can get damaged.
  • This means that they are no longer able to convert vibrations into impulses
  • Thus they can’t hear these sounds
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15
Q

SP4f - What is the human range of hearing?

A

20Hz - 20,000 Hz

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16
Q

SP4f - What is ultrasound?

A

Sound above 20,000 Hz

17
Q

SP4f - How can boats use ultrasound in sonar equipment?

A
  • To find the depth of the water beneath them.
  • They fire off an ultrasound wave at 1500m/s.
  • They time how long it takes to return.
  • They use d = s x t to find out the distance hte wave travelled and divide it by 2 to find the depth of the water
18
Q

SP4f - How is ultrasound used in scans?

A
  • A probe emits ultrasound waves
  • Gel is used to stop it from reflecting
  • Some waves are reflected when they meet bones, fat, tissue etc.
  • The probe also detects these refelected waves
  • It sends these as impulses to the computer
  • The ultrasound imaging machine detcts the frequency of the impulses turning it into an image
19
Q

SP4f - Why is an ultrasound scan more beneficial for scanning a foetus?

A
  • Other scans such as PET and CT would release radiation
  • This could harm the foetus causing mutations
20
Q

SP4g - What is infrasound?

A

Sound below 20Hz

21
Q

SP4g - What are the two types of seismic waves and what is the difference?

A
  • P waves: Longitudinal
  • S waves: Transverse
22
Q

SP4g - What are seismic waves?

A

Vibrations produces by earthquakes

23
Q

SP4g - Why are P waves more useful than S waves?

A
  • P waves are longitudinal while S waves are transverse
  • S waves can only be transmitted by solids but P waves can go through all through states
  • The earth has a liquid outer core
  • S waves fired from a point can’t go throuhg the liquid core but P waves can
  • This means that S waves have a larger shadow zone
  • Using the idea that S waves can’t go through liquids and P waves can, scientists were able to find out about the structure of the earth
24
Q

SP4g - What is a shadow zone?

A

The area where a wave cannot reach when fired from a point

25
Q

SP4g - What is the key thing to remember about seismic waves as they pass through the earth?

A

They get refracted

26
Q

SP4g - Why may there still be weak P waves even in the shadow zones?

A

They can be reflected by the solid inner core

27
Q

SP4g - How can seismic waves be used to detect earthquakes?

A

Seismic waves can be detected by seismometers and give information about where earthquakes are originating

Edexcel GCSE Physics (17 decks)

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