Waves Flashcards

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1
Q

What do waves transfer

A

Energy

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2
Q

What don’t waves transfer

A

Matter

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3
Q

How is it proven that waves only transfer energy

A

shown in the sea, where buoys stay still despite waves passing by them – the waves move, but not the particles

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4
Q

What does wavelength mean

A

The distance between the same points on two consecutive waves

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5
Q

What does frequency mean

A

The number of waves that pass a single point per second

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6
Q

What does amplitude mean

A

Distance from equilibrium line to the trough

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7
Q

What is a period

A

The time taken for a whole wave to completely pass a point

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8
Q

What does a wavefront mean

A

The plane in which the wave travels (the direction of the wave

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9
Q

How to do workout the velocity of a wave

A

wave speed (m/s) = frequency (Hz) ×
wavelength (m)
(v = f × λ)

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10
Q

What is a transverse wave

A

the oscillations are perpendicular to the direction of energy transfer

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11
Q

What is a longitudinal wave

A

the oscillations are parallel to the direction of energy transfer

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12
Q

What is an example of a transverse wave

A
  • any electromagnetic wave
  • seismic S waves
  • water waves
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13
Q

What’s an example of a longitudinal wave

A
  • Sound waves
  • P waves
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14
Q

How do you measure the velocity of soundwaves in the air

A
  1. Make a noise at ~50m from a solid wall
  2. Record how long it takes for the echo to be heard
  3. Use speed = distance / time
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15
Q

How do you measure the velocity of soundwaves in the air (using a microphone)

A
  1. Have two microphones connected to a data logger at a large distance apart
  2. Record the time difference between the sound passing from one to the other
  3. Use speed = distance/time
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16
Q

How do you measure the velocity of soundwaves on water surface (using a stroboscope)

A
  1. Use a stroboscope which has the same frequency as water waves
  2. Measure the distance between the ‘fixed’ ripples
  3. Use 𝑣 = 𝑓𝜆
17
Q

How do you measure the velocity of soundwaves on water surface

A
  1. Move a pencil along the paper at the same speed as a wavefront
  2. Measure time taken to draw the line / measure the length of the line
  3. Use speed = distance/time
18
Q

Describe refraction

A
  • waves pass from one medium to another
  • If passing into a denser medium (i.e air to glass) wave will refract TOWARDS the normal
19
Q

Describe what happens when a wave is refracted into a denser medium

A
  • Speed of wave decreases
  • Wavelength decreases
  • Energy is constant
20
Q

Describe reflection

A

Waves reflect off a flat surface

21
Q

How do different surfaces affect reflection

A

The surface: * smoother the surface the stronger the reflected wave is
* Rougher the surface the more the light will scatter

22
Q

What is transmission

A

When waves pass through a transparent material

23
Q

What is absorption

A

Energy taken in by a material

24
Q

Why may certain substances absorb, transmit, refract or reflect waves differently

A

Due to different wavelengths

25
Q

How does the ear work

A
  1. Sound causes air particles in our ear canal to vibrate and hit the eardrum.
  2. The eardrum vibrates, passing these vibrations to three small ear bones: hammer, anvil, and stirrup.
  3. The stirrup hits the cochlea, converting vibrations into an electrical signal sent to the brain via the auditory nerve. Our brain then translates this signal into sound.
26
Q

What are compressions

A

regions of higher density

27
Q

What are rarefactions

A

Regions of lower density

28
Q

What is the range of frequency a human can hear

A

20Hz to 20000Hz

29
Q

What is the process of sound going through different states of matter

A

Wavelengths get longer as speed increases in higher density mediums (solids)

Wavelengths get shorter as speed decreases in lower density mediums (air)

30
Q

What are frequencies under 30 called

A

infrasounds

31
Q

How is ultrasound used for foetal scanning

A

ultrasound waves partially reflect at each surface boundary, this can be used to work out the distances and therefore an image of the foetus

32
Q

How is ultrasound used for sonar

A

Pulse of ultrasound is sent below a ship, and the time taken for it to reflect and reach the ship can be used to calculate the depth

33
Q

Explain how hearing processes only work over a limited
frequency range

A

Higher the frequency = more energy transferred
Damages cells in the ear

34
Q

What has a frequency below 20Hz

A

Infrasound

35
Q

What are P waves and what can it pass through

A

Longitudinal
Can pass through solids and liquids

36
Q

What are S waves and what can they pass through

A

Transverse
Solids

37
Q

How can S and P waves be used to explore the earths core

A

On the opposite side of the Earth when an earthquake occurs only P waves are detected, suggesting the core of the Earth is liquid – hence no S waves can penetrate it