SP4 - Waves ✓ Flashcards Preview

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Flashcards in SP4 - Waves ✓ Deck (27)
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1

SP4a - Describe a transverse wave, giving examples.

  • 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

2

SP4a - Describe a longitudinal wave, giving examples.

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

3

SP4a - Descirbe the following features of a transverse wave:

  1. Frequency
  2. Period
  3. Wavelength
  4. Amplitude

  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

4

SP4b - What are the two formulas for wave speed?

v = d/t

(Velocity = distance ÷ time)

v = f x λ

(Velocity = frequncy x wavelength)

5

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

  • 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.

6

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

  • 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

7

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

  • 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

8

SP4c - How does refraction occur?

  • 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

9

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

  • 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

10

SP4d - What are the definitions of the following:

  • Reflect
  • Refract
  • Transmit
  • Absorb

  • 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

11

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

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

12

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

  • 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

13

SP4e - How does the cochlea work?

  • 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)

14

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

  • 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

15

SP4f - What is the human range of hearing?

20Hz - 20,000 Hz

16

SP4f - What is ultrasound?

Sound above 20,000 Hz

17

SP4f - How can boats use ultrasound in sonar equipment?

  • 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

SP4f - How is ultrasound used in scans?

  • 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

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

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

20

SP4g - What is infrasound?

Sound below 20Hz

21

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

  • P waves: Longitudinal
  • S waves: Transverse

22

SP4g - What are seismic waves?

Vibrations produces by earthquakes

23

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

  • 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

SP4g - What is a shadow zone?

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

25

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

They get refracted

26

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

They can be reflected by the solid inner core

27

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

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