SP4 - WAVES Flashcards
1
Q
What can waves do?
A
Transfer energy between stores.
2
Q
What can waves be described as?
A
Oscillations, or vibrations about a rest position.
3
Q
How do sound waves cause particles to move?
A
The sound waves cause air particles to vibrate back and forth.
4
Q
How do ripples cause water particles to move?
A
They cause water particles to vibrate up and down.
5
Q
What is the direction of the oscillations the difference of?
A
The difference between longitudinal or transverse waves.
6
Q
In what direction are vibrations in a longitudinal wave?
A
Parallel to the direction of the wave travel.
7
Q
In what direction are the vibrations in a transverse wave?
A
The vibrations are at right angles (perpendicular) to the direction of the wave travel.
8
Q
What do mechanical waves cause?
A
Oscillations of particles in a solid, liquid or gas and must have a medium to travel through.
9
Q
What is a medium?
A
A material through which a wave can be transmitted (propagate).
10
Q
What can mechanical waves be?
A
Longitudinal and Transverse
11
Q
What do electromagnetic waves cause?
A
Oscillations in electrical and magnetic field.
12
Q
All electromagnetic waves are what?
A
Transverse.
13
Q
What does rest position mean?
A
The undisturbed position of particles or fields when they are not vibrating.
14
Q
What is displacement in terms of describing a wave?
A
The distance that a certain point in the medium has moved from its rest position.
15
Q
What is the peak?
A
The number of waves passing a point each second. The highest point is above the rest position.
16
Q
What is the trough?
A
The lowest point below the rest position.
17
Q
What is amplitude?
A
The maximum displacement of a point of a wave from its rest position.
18
Q
What is wavelength?
A
Distance covered by a full cycle of the wave. Usually measured from peak to peak, or trough to trough.
19
Q
What is the time period?
A
The time taken for a full cycle of the wave. Usually measured from peak to peak, or trough to trough.
20
Q
What is frequency?
A
The number of waves passing a point per second.
21
Q
Name 3 examples of longitudinal waves
A
Sound waves
Ultrasound waves
Seismic P- waves
22
Q
What do longitudinal waves show areas of?
A
Compression and rarefaction.
23
Q
What is compression?
A
Regions of high pressure due to the particles being close together.
24
Q
What is rarefaction?
A
Regions of low pressure due to the particles being spread further apart.
25
Name 3 examples of a transverse wave.
Ripples on the surface of water
Electromagnetic waves- light waves, microwaves, radio waves
Seismic S- waves.
26
In what direction is energy transferred in transverse waves?
From left to right.
27
Are the particles transported along a transverse wave ?
No.
28
What happens to the particles?
They move up and down as the wave is transmitted through the medium.
29
How can the time period of a wave be calculated?
Time period= 1/ frequency
30
Calculate the time period of a wave with a frequency of 400Hz
1/400 = 0.0025s
31
How do you calculate wave speed?
Frequency x Wavelength
32
What is the speed of a wave with a frequency of 0.2 Hz and a wavelength of 25m
5m/s
33
What is sound?
A mechanical longitudinal wave.
34
How is the wave passed on?
By collisions between particles, so the speed the wave moves depends of the density of the particles.
35
What does constant speed mean?
That the wavelength will be proportional to the wave velocity.
36
What travels faster through air, light or sound?
Light
37
How does sound get to someone's ear, in terms of particles?
When sound is created, the air particles vibrate and collide with each other, causing the vibrations to pass between air particles. The vibrating particles pass the sound through to a person's ear and vibrate to the ear drum.
38
How can the speed of sound be calculated?
Speed = distance/ time
39
An observer 400m away records a 1.2s time difference between seeing the hand signal and hearing the bang of the starting pistol? What is the speed of sound?
400/1.2 = 333 m/s
40
Why is this experiment flawed?
Humans don't use stop clocks identically. One person might stop the timer a fraction of a second later than another person. The values are dependent on the reaction times of the person with the stopwatch so the results are never entirely accurate.
41
What is the method for measuring the frequency, wavelength and speed of waves in a ripple tank?
1. Set up a ripple tank with water of a certain depth.
2. Adjust the height of the wooden rod so that it just touches the surface of the water.
3. Switch on the lamp and motor and adjust until low frequency waves ca be clearly observed.
4. Measure the length of a number of waves then divide by the number of waves to record wavelength.
5. Count the number of waves passing a point in ten seconds then divide by ten to record frequency.
6. Calculate the wave speed using wave speed = frequency x wavelength.
42
What are hazards to this method and what are there consequences and how can they be controlled?
Electrical components near water - shock, damage to goods- Secure electrical components before adding water taking care not to splash.
43
What is the method used for finding out the frequency, wavelength and wave speed in a solid?
1. Hang a metal rod across a clamp.
2. Hit one end of the rod with a hammer.
3. Hold a smartphone with an app that measures frequency near the end of the rod.
4. Record the peak frequency from the phone app.
5. Measure the length of the metal rod and record the length.
6. Calculate the speed of the sound waves in the rod using the frequency and wavelength recorded.
44
What are hazards with this method and what are the consequences and how can they be controlled?
Dropping rod or hammer - injury from falling objects - take care to hold equipment carefully.
45
What is the average speed of sound through air?
330m/s
46
Why can't sound travel through a vacuum.
Because there aren't any particles to carry the vibrations.
47
What is a vacuum?
A volume that contains no matter.
48
What can happen when waves are transmitted at a boundary between 2 materials?
They may change direction.
49
What does transmitted mean?
A wave is passed across or through a material.
50
What is refraction?
The change in direction of a wave at a boundary. All wave types can be refracted.
51
State and explain one factor that affects the speed of a wave.
The density of a material affects the speed of the wave. If an object goes from less dense to more dense, it bends away from the normal. If it goes from more dense to less dense, it bends towards the normal.
52
What happens to a fast wave?
It moves faster and away from the normal.
53
What happens to a Slow wave?
It moves slower and towards the normal.
54
What can happen to waves at a boundary between 2 materials?
They can be reflected, transmitted or absorbed.
55
What does absorbed mean?
Energy is 'taken - in' by the material and the internal energy of the material will increase. Wavelength has a big effect on how much of a wave's energy is reflected, absorbed or transmitted at an inference.
56
What happens when light passes from a less dense to a more dense substance?
The light is refracted towards the normal.
57
What happens when the light passes from a more dense to a less dense substance?
The light is refracted away from the normal.
58
The type of wave...
its properties such as wavelength and the difference between the two media will determine what happens to most of the wave energy.
59
What property of a wave has a big effect on how much of a wave's energy is reflected, absorbed or transmitted at an interface?
Wavelength.
60
What can happen to waves at the boundary between two different materials?
They can be reflected.
61
What does the reflection of sound cause?
Echoes.
62
What does the law of reflection state?
angle of incidence = angle of reflection.
63
The angles of incidence and reflection are measured between...
the light ray and the normal.
64
What is refraction?
The change in direction of a wave at such a boundary.
65
For a given frequency of light the wavelength is...
Proportional to the wave speed.
66
What will happen if a wave slows down?
Its wavelength will decrease.
67
The amount that the wavelength is changed...
Affects the amount the direction changes.
68
What does the amount of wavelength depend on?
the differences between the material on each side of the interface.
69
Waves arriving at the interface (boundary) between 2 materials can be...
reflected, transmitted or absorbed.
70
What does transmitted mean?
A wave is passed across or through a material (medium).
71
Wavelength has a big affect on...
How much a wave's energy is reflected, absorbed or transmitted at an interface.
72
What type of waves are sound waves?
Longitudinal.
73
When travelling through air, what is the average speed of sound?
330m/s
74
Why can't sound travel through a vacuum?
Because there are no particles to carry the vibrations.
75
How do humans hear sound?
Sound waves enter the ear canal and cause the eardrum to vibrate. Three small bones transmit these vibrations to the cochlea. Hair cells in the cochlea detect these vibrations and the cochlea turns them into electrical signals which pass through the auditory nerve to the brain, where they are interpreted as sound.
76
The frequency of a sound...
Is related to the pitch that is heard:
high frequency sound waves are high pitched
low frequency sound waves are low pitched.
77
The amplitude of a sound wave is...
related to the volume of the sound:
high amplitude sound waves are loud
low amplitude sound waves are quiet.
78
What is the range of normal human hearing frequencies?
20Hz to 20000Hz
79
What is infrasound?
Sound with a frequency below 20Hz
80
What is ultrasound?
Sound with a frequency above 20000Hz.
81
Name 4 uses of ultrasound.
Breaking kidney stones
Cleaning jewellery
Foetal scanning
Detecting cracks in machinery.
82
What does ultrasound imaging do?
Creates a picture of something that cannot be seen directly. Such as a baby in the mother's womb.
83
What do these uses rely on?
Ultrasound waves meeting the boundary between 2 different materials. When this happens:
1. Some of the ultrasound waves are reflected at the boundary.
2. The time taken for the waves to leave a source and return to a detector are measured.
3. The depth of the boundary can be determined using the speed of sound in the material and the time taken.
84
What can high frequency sound waves be used to detect?
Objects in deep water and to measure water depth.
85
What is the equation to work out distance using SONAR?
Distance = speed x time/2
86
What are the two types of seismic waves?
S-waves
| P-waves
87
What state of matter can S-waves pass through?
Solids. S-waves are not detected on the opposite side of the Earth - this suggests that the mantle has solid properties, but the outer core must be liquid.
88
What states of matter can P-waves travel through?
Solids and liquids. P-waves are detected on the opposite side of the Earth. Refractions between layers cause two shadow zones, where no P-waves are detected - the size and positions of these shadow zones indicate there is a solid inner core.
89
What is a shadow zone?
Parts of the earth when no S or P-waves are detected.
