GCSE Edexcel Physics > 4: Waves > Flashcards

4: Waves Flashcards

(102 cards)

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1
Q

What do waves transfer

A

Energy and information

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2
Q

How is energy and information transferred by waves through a medium

A

The particles of the medium vibrate and transfer energy and information between each other

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3
Q

Ripples analogy for waves

A

When you drop a twig into a calm pool of water, ripples form on the surface. The ripples don’t carry the twig away with them though

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4
Q

Amplitude of a wave

A

The displacement from the rest position to a crest or trough

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5
Q

Crest

A

The highest displacement from the rest position in a wave

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6
Q

Trough

A

The lowest displacement from the rest position in a wave

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7
Q

Wavelength

A

Full cycle of a wave (distance from crest to crest)

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8
Q

Frequency

A

The number of complete cycles passing a certain point per second

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9
Q

1 Hz

A

1 wave per second

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10
Q

What is frequency measured in

A

Hertz

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11
Q

Hertz abbreviation

A

Hz

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12
Q

Period of a wave

A

The number of seconds it takes for a full cycle of the wave to pass a point

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13
Q

How to calculate period

A

1/frequency

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14
Q

Transverse wave

A

The vibrations are perpendicular to the direction the wave travels

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15
Q

Examples of transverse waves

A

-EM waves
-Seismic S-waves
-Ripples in water

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16
Q

Longitudinal wave

A

The vibrations are parallel to the direction the wave travels

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17
Q

What do longitudinal waves do to a medium they travel through

A

Squash up and stretch out the arrangement of particles in the medium

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18
Q

Compression

A

An area with lots of particles (high pressure) in a longtitudinal waves through

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19
Q

Rarefraction

A

An area with less particles (low pressure) in a longitudinal waves through

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20
Q

Examples of longitudinal waves

A

-Sound waves
-Seismic P-waves

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21
Q

Wave speed equation

A

Wave speed = frequency x wavelength

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22
Q

Describe an experiment to measure the speed of sound in air

A

1- Attatch a signal generator to a speaker. Attatch two microphones to an oscilloscope.
2- Play sound from the signal generator and turn the oscilloscope on.
3- Aligin both microphones next to the speaker, then move one away from the other slowly until the two waves are aligned on the oscilloscopes display (so they are 1 wavelength apart) and measure the distance between them
4- Work out the speed of sound using the generated frequency of the signal generator x the distance between the microphones

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23
Q

Signal generator

A

Can generate waves of specific chosen frequencies

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24
Q

Describe an experiment to measure the speed of water ripples

A

1- Attatch a signal generator to the dipper of a ripple generator. Dim the lights and turn on the strobe light.
2- Change the frequency of the strobe light until the wave pattern on the screen appears to freeze
3- The distance between each shadow line is a wavelength so multiply this by the frequency of the strobe light to find the speed

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25
Why can you measure the wavelength of the shadows of ripples on a screen when they appear to stop moving during the ripple tank experiment
The frequency of the waves matches the frequency of the strobe light so they are being lit at the same point of their cycle each time
26
How to improve the ripple tank experiment
Measure the distance between 10 waves and divide by 10 to find the average wavelength
27
Experiment to find the speed of waves in solids
1- Measure and record the length of a metal rod. Hold it by clamps next to a microphone attatched to a computer. 2- Tap the rod with the hammer. Write down the peak frequency displayed by the computer. 3- Repeat for an average peak frequency. Multiply this by the rod’s length x2 to find the speed of sound.
28
Describe what happens when you hit a rod with a hammer
Waves are produced along the rod which make the rod vibrate and produce sound waves in the air around the rod
29
What can happen when a wave meets a boundary
-Absorption -Transmission -Reflection
30
Absorption
When the wave transfers energy to the material’s energy stores
31
Transmission
The wave carries on travelling through the new material which can lead to refraction
32
Reflection
The incoming ray is sent back away from the second material
33
Refraction
When a wave hits a boundary at an angle and changes speed, causing a change in direction
34
What happens when a wave slows down when hitting a boundary at an angle
It bends towards the normal
35
What happens when a wave speeds up when hitting a boundary at an angle
It bends away from the normal
36
How does the wavelength of an EM wave affect its refraction
The shorter the wavelength the more it bends
37
Dispersion
When the wavelengths of a wave spread out (light prism)
38
What causes dispersion
Different wavelengths of EM radiation refract more or less
39
What happens so the speed of EM radiation when entering a less dense material
Speeds up
40
What happens to the speed of EM radiation when entering a denser material
Slows down
41
How does the amount the speed changes affect the refraction
The greater the change in speed, the more the wave refracts
42
Why isn’t a wave refracted when it is travelling along the normal
Because to be refracted it must hit the boundary at an angle
43
What happens to the frequency of the wave at a boundary
It stays the same
44
What happens to the wavelength of the wave at a boundary
It changes
45
What happens to the wavelength if a wave slows down
Decreases
46
What happens to the wavelength when a wave speeds up
Increases
47
Why does a wave refract
When one part of a wavefront crosses a boundary and changes speed, that part is travelling at a different speed to the rest of the wavefront front so the wave bends
48
Normal
An imaginary line perpendicular to the surface at the point of incidence
49
Incidence
When the wave hits the boundary
50
How should you draw the normal
A dotted line
51
Incident ray
The ray that hits the boundary
52
Angle of incidence
The angle between the incident ray and normal
53
How to improve the refraction experiment
-Do it in a dim room -The ray should be thin -Repeat 3 times with the same angle of incidence to find an average
54
Why should the refraction experiment be done in a dim room
So that you can clearly see the ray
55
Why should the ray of light be thin in the refraction experiment
So that you can clearly see the middle of the ray when tracing and measuring angles from it
56
Describe how to investigate the refraction of light in a glass block
1- Place a rectangular glass block on a piece of paper and trace around it. Use a ray box to shine a ray of light at the middle of one side of the block. 2- Trace the incident and emergent ray. Remove the block and connect the two lines to show the path of the refracted ray 3- Draw a normal where the light entered with an angle of incidence between the incidence ray and normal and an angle of refraction between the refracted ray and normal. 4- Repeat this for where the ray emerges from the block and measure both incidence and refracted angles with a protractor
57
How to make the ray thin in the refraction experiment
Use a ray box
58
Explain what happens when you shine light at the middle of a glass block at an angle
-Light first bends towards the normal as it slows down when it enters the block (because glass is denser than air). -When leaving the block, the light bends away from the normal as it speeds up (because air is less dense than glass)
59
Law of reflection
Angle of incidence = angle of reflection
60
Total internal reflection
When a wave crosses a boundary and all of it is reflected back into the material
61
When does total internal reflection happen
When a wave travels through a dense material to a less dense material AND the angle of incidence is larger than the critical angle
62
Critical angle
-The angle which an angle of incidence must be greater than to be totally internally reflected -Each boundary has its own different critical angle
63
Specular reflection
When waves are all reflected in a single direction by a smooth surface
64
Diffuse reflection
When waves are reflected by a rough surface in different directions
65
Explain specular reflection
All of the normals are parallel as the surface is flat so each ray is reflected the same
66
Explain diffuse reflection
The normals for each incident ray are different as the surface is bumpy so each ray is reflected differently
67
What causes sound waves
Vibrating objects
68
What happens when a sound wave travels through a solid
It causes the particles to vibrate. These particles hit the next particles causing them to vibrate too, passing the sound wave
69
Order the states of matter from fastest to slowest for sound waves travelling through them
-Solid -Liquid -Gas
70
Echo
A reflected sound wave
71
Why can’t sound travel in a vacuum
There are no particles to move or vibrate
72
Cochlea
Turns vibrations into electrical signals which are sent to your brain
73
How is human hearing limited
-The size and shape of our eardrum -The structure of the parts within the ear that vibrate to transmit the sound wave
74
Eardrum
Vibrates when sound waves reach it
75
Ossicles
The tiny bones where vibrations from the eardrum pass through before the semicircular canals
76
Semicircular canals
Where vibrations from the ossicles travel through before the cochlea
77
Auditory nerve
Sends electrical signals from the cochlea to the brain
78
What happens to sound in your brain
The amplitude of the sound wave is interpreted as volume and the frequency of a sound wave is interpreted as pitch
79
Infrasound
Sound waves we cannot hear as they are too low in frequency
80
Maximum frequency of infrasound
20Hz
81
How is infrasound used
-Some animals communicate using infrasound -Natural disasters produce infrasound -Earthquakes produce infrasound
82
Why is animal communication through infrasound important for scientists
They can detect infrasound and use it to track animals for conservation purposes
83
Why is the production of infrasound waves from natural disasters important
Scientists can monitor infrasound to predict events
84
Ultrasound
Sound waves we cannot hear as they are too high in frequency
85
Minimum frequency of an ultrasound wave
20,000Hz
86
Partial reflection
When some of the wave is reflected and some of the wave is transmitted at a boundary
87
What happens to ultrasound waves at boundaries
They are partially reflected
88
Why is it important that ultrasound waves are partially reflected at boundaries
You can measure how far away boundaries are from the time between ultrasound detections
89
Ultrasound uses
-Medical imaging -Industrial imaging -Echo sounding
90
How is ultrasound used in the prenatal scanning of a foetus
1- Ultrasound waves are transmitted through the body and are partially reflected and detected at boundaries between two media (like the fluid in the womb and the skin of the foetus). 2- The exact timing and distribution of these echoes are processed by a computer to produce a video image of the foetus
91
What is ultrasound used in industrial imaging to detect
Flaws in objects such as pipes, wood or metal
92
How is ultrasound used in industrial imaging
Ultrasound waves are usually reflected by the far side of the material. If there is a flaw inside the material, the wave will be reflected sooner.
93
Echo sounding
A type of sonar where boats and submarines use ultrasound to detect the distance to the seabed or locate objects in deep water
94
Seismometers
Devices which can detect seismic waves
95
Seismic waves
Waves produced by earthquakes
96
How have seismologists determined the structure of the Earth
They have noted where seismic waves are detected and where they are not, as well as the path of their refraction
97
Which states can seismic P-waves travel through
Solids and liquids
98
Speed of seismic P-waves compared to seismic S-waves
Faster
99
Which states can seismic S-waves travel through
Solids
100
Speed of seismic S-waves compared to seismic P-waves
Slower
101
How do we know that the outer core is liquid
-There is a large area seismic S-waves cannot reach and they cannot travel through liquid -When there is a drastic change in density (solid to liquid) the refraction changes greatly too, causing a kink in the path of seismic P-waves’ refraction
102
How do we know that the inner core is solid
Seismic P-waves have two large kinks in their path of refraction suggesting that the state of the Earth’s layers changes twice
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