Waves Flashcards
(141 cards)
1
Q
What are the two types of wave?
A
Longitudinal and transverse
2
Q
What do waves do with energy? Give an example.
A
All waves transfer energy from one place to another.
E.g. if a stone is dropped into a pond, ripples travel outwards carrying the energy. The water does not travel outwards otherwise it would leave a hole in the middle. The energy moves on but the matter remains.
3
Q
What sort of waves are the ripples in the surface of water?
A
Transverse
4
Q
How do the particles that make up a wave move?
A
They oscillate about a fixed point. In doing so they pass energy onto the next particles which oscillate and so on.
5
Q
Give an example of a transverse wave.
A
Water waves
6
Q
What is a transverse wave?
A
It is a wave where the oscillations are perpendicular to the direction of energy transfer.
7
Q
How can transverse be demonstrated with a rope or slinky?
A
You can move a rope or slinky up and down vertically, the wave then moves horizontally.
8
Q
Give an example of a longitudinal wave?
A
Sound wave
9
Q
What are longitudinal waves?
A
A longitudinal wave is where the oscillations are parallel to the direction of energy transfer.
10
Q
How can a longitudinal wave be demonstrated with a slinky or rope?
A
This can be demonstrated by moving a slinky or rope backwards and forwards horizontally- the wave also moves horizontally.
11
Q
What do longitudinal waves show?
A
Areas of compression (where the waves are tight) and areas of rarefaction (where the waves are further apart).
12
Q
What do all waves have?
A
A frequency, amplitude, wavelength, period, trough, wavelength, peak
13
Q
What is frequency?
A
The number of waves passing a fixed point per second
14
Q
What is frequency measured in?
A
Hertz (Hz)
15
Q
What is amplitude?
A
The maximum displacement that any particle achieves from its undisturbed position in metres (m)
16
Q
What is a period?
A
The time taken for one complete oscillation in seconds
17
Q
What amplitude and the period seen as when observing a wave?
A
Amplitude- the height
The period- time taken for one wave to pass a fixed point.
18
Q
What does amplitude indicate?
A
The amount of energy a wave is carrying. The more energy, the higher the amplitude.
19
Q
What is wave speed?
A
The speed at which the energy is transferred (or the wave moves) through a medium.
20
Q
Why is the equation for wave speed sometimes called the ‘wave equation’?
A
Because all waves obey it
21
Q
What happens when waves are transmitted from one medium to another?
A
Their speed and therefore their wave length changes e.g. water waves travelling from deep to shallow water.
22
Q
What happens to the frequency of a wave when it moves from one medium to another?
A
The frequency does not change because the same number of waves is still being produced by the source per second.
23
Q
What is as a result of the fact that all waves obey the wave equation?
A
The speed and wavelength of waves are directly proportional:
- Doubling the speed doubles the wavelength
- Halving the speed halved the wavelength
24
Q
Where are waves reflected?
A
At the boundary between two different materials.
25
What happens when waves meet a boundary between one medium and another?
They can be reflected, refracted, absorbed or transmitted
26
What sort of diagrams are used to show waves being reflected, refracted, absorbed or transmitted?
Ray diagrams
27
What do you need to take into account when drawing a ray diagram?
- Rays must be drawn with a ruler!
- Each straight section of ray should have an arrow to indicate the direction of movement
- Where a ray meets a boundary a ‘normal’ should be drawn at right angles to boundary
- All relevant angles should be labelled
28
What happens to the angles when waves are reflected at a surface?
The angle of incidence is equal to the angle of reflection
29
What is refraction?
Refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium.
30
What does the direction of refraction depend on?
- The angle at which the wave hits the boundary
| - The materials involved
31
What is a material’s refractive index?
For light rays, the way in which the material affects refraction is called it’s refractive index.
32
What happens when light travels from a material with a low refractive index to one with a higher refractive index?
It bends towards the normal
33
What happens when light travels from a material with a high refractive index to one with a lower refractive index?
It bends away from the normal
34
Why does refraction happen?
It is due to the difference in wave speed in the different mediums
35
What happens when a light wave enters a medium in which it travels slower at an angle?
- The first part of the light wave to enter the medium slows down
- The rest of the wave continues at s higher speed
- This causes the wave to change direction towards the normal.
36
What is the normal?
A normal is an object such as a line or vector that is perpendicular to a given object.
37
In a sound wave what does the amplitude relate to?
The loudness
38
What do the frequency and wavelength of a sound wave relate to?
The pitch- the higher the frequency, the higher the pitch.
39
What is the normal hearing range for a human?
20 Hz - 20 KHz (20,000 Hz)
40
What states can sound travel through?
Liquids and solids as well as air
41
Why does sound happen?
In any medium sound is due to the vibration of the particles that make up the medium.
42
What do the oscillations caused by a sound wave do to an object?
These oscillations can cause the entire object to vibrate with the same frequency as the sound wave.
43
When a sound wave is converted to vibrations what happens in terms of frequency?
The conversion of sound waves to vibrations only occurs over a limited range of frequencies, the range of frequencies converted is dependent of the structure of the object.
44
How is sound heard?
Within the ear, sound waves cause the ear drum and other structures to vibrate and it is this vibration that is heard as sound.
45
What limits human hearing?
The limited range conversion.
46
What are some example of sound being converted into a vibration?
In the ear drum, by a microphone, a glass being shattered by an opera singer
47
What is the frequency of ultrasonic waves?
Ultrasonic waves have a frequency greater than 20KHz so they cannot be heard by humans.
48
What happens when an ultrasonic wave meets a boundary between two different media?
It is partially reflected.
49
How do you measure how far a boundary is?
By measuring the time taken for reflected ultrasonic waves to return to a detector.
50
How is ultrasound uses in industry?
Detecting defects in materials without cutting into them. These defects could be manufacturing faults (e.g. cracks and air bubbles) or damage (e.g. corrosion).
51
How is ultrasound used in medicine?
- Pre-natal scanning
- Detection of kidney stones/ tumours
- Producing images of damaged ligaments and muscles.
52
What is echo-sounding or sonar?
The use of ultrasonic waves for detecting objects in deep water and measuring the depth of water.
53
What does echo sounding/ sonar involve?
It involve sending an ultra sounding pulse into the water, which is then reflected back when it hits a surface.
54
How do you calculate the distance being travelled by an ultrasound wave?
The time between the pulse being sent and the reflection being detected is used to calculate the distance being travelled by the sound wave:
Distance= speed x time
55
What two types of seismic waves are produced during an earth quake?
- P-waves (Primary)
| - S-waves (Secondary)
56
What are seismic waves?
An elastic wave in the earth produced by an earthquake or other means.
57
What are the properties of P-waves?
- Are longitudinal
- Travel at the speed of sound and are twice as fast as S-waves
- Travel at different speeds through solids and liquids
58
What are the properties of S-waves?
- Are transverse
| - Not able to travel through liquids
59
How can P-waves and S-waves provide evidence about the location of the earthquake?
When seismic waves are produced, the difference in time between the arrival of P-waves and S-waves at different detectors can provide evidence about the location of the earthquake and the material the have travelled through.
60
Which directions do seismic waves travel during an earthquake?
Seismic waves travel outwards from the earthquake and are capable of travelling all the way through the earth.
61
What sort of path do seismic waves travel in?
In a curved path through the earth, due to the Earth increasing in density with depth.
62
Why are detectors placed around the earth?
To measure when and where the two different waves arrive.
63
How do S-wave shadow zones provide evidence of the size of the Earth’s core?
S-waves are not able to travel through the liquid outer core of the Earth. This results in a large shadow zone on the opposite side of the Earth to where it originated. This shadow provides evidence of the side of the Earth’s core.
64
How do P-wave shadow zones determine the size and composition of the inner and outer core?
P-waves are able to travel through the liquid outer core. However, they are refracted at the boundary between the semi-solid mantle and the liquid outer core. They are refracted again at the boundary between the liquid outer core and the solid inner core. These refractions result in P-wave shadow zones. The study of these shadow zones is used to determine the size and composition of the inner and outer core.
65
What type of wave are electromagnetic waves?
Transverse
66
How do electromagnetic waves transfer energy?
They transfer energy from the source of the waves to an absorber.
67
What do all electromagnetic waves do?
They form a continuous spectrum and all types of electromagnetic wave travel at the same velocity through a vacuum (space) or air.
68
How does the electromagnetic spectrum extend?
It extends from a low frequency, low energy waves to high frequency, high energy waves. The waves that form the electromagnetic spectrum are grouped in terms of their wavelength and their frequency going from long to short wavelength (or from low to high frequency).
69
What are the groups of electromagnetic waves?
- Radio
- Microwave
- Infrared
- Visible light (red to violet)
- Ultra violet
- X-rays
- Gamma rays
70
How are the groups in the electromagnetic spectrum ordered?
Long wavelength - short wavelength
Low Frequency - High Frequency
Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma rays
71
What sort of light can human eyes detect?
Visible light
72
How does the wavelength of an electromagnetic wave affect its uses?
The wavelength of an electromagnetic wave effects how it is absorbed, transmitted, reflected or refracted by different substances. This affects its uses.
73
What are radio waves used for?
Television, radio and Bluetooth
74
How are radio waves adapted to their uses?
They are low energy waves therefore they are not harmful and ideal for radio transmission.
75
What are microwaves used for?
Cooking food, satellite communication
76
How are microwaves adapted to their uses?
They travel in straight lines through the atmosphere which makes them ideal for transmitting signals to satellites in orbit and back down to receivers.
77
What are the uses of infrared waves?
Electrical heaters, cooking food, infrared cameras
78
How are infrared waves adapted to their uses?
Electric heaters, grills and toaster glow red hot as electricity passes through them. This transmits infrared energy absorbed by the food and converted back into heat.
79
What are the uses of visible light?
Fibre optic communications
80
What are the adaptations of visible light?
Visible light travels form the optical fibres from one end to that other without being lost through the sides.
81
What are the uses of ultraviolet waves?
Energy efficient lightbulbs, security marking, sun beds
82
How are ultraviolet waves adapted to their functions?
In energy efficient lightbulbs UV waves are produced by the gas in the bulb when it is excited by the electric current. These UV waves are absorbed by the coating on the bulb, which fluoresces giving of visible light.
83
What are the uses of X-rays?
Medical images and treatments
84
What are the adaptations of X-rays for their functions?
They are able to penetrate soft tissue but not bone.
| A photographic plate behind a person will show where the shadows where bones are.
85
What are the uses of gamma rays?
Sterilising food, treatment of rumours.
86
What are the adaptations gamma rays?
Gamma rays are the most energetic of all electromagnetic waves and can be used to destroy bacteria and tumours.
87
How are radio waves caused?
Caused by oscillations in electrical circuits i.e. alternating current
88
How is radio signal produced?
The frequency of the radio wave produced matches the frequency of the electrical oscillation.
89
How is radio signal received?
When radio waves are absorbed by a conductor they may create an alternating current with the same frequency as the radio wave, this is how the signal is received.
90
When is an electrical signal that matches the wave in terms of radio signals produced?
When the oscillation is induced in an electrical circuit.
91
What can changes in atoms and the nuclei of atoms do to EM waves?
They can result in EM waves being generated or absorbed over a wide frequency range.
92
How can EM waves be generated?
- Electrons moving between energy leaves as a result of heat or electrical excitation can generate waves e.g. infrared waves, visible light, ultraviolet waves and X-rays.
- Changes in the nucleus of an atom can generate waves e.g. an unstable nucleus can give out excess energy as gamma rays.
93
What sort of waves carry enough energy to have hazardous effects on the human body?
Ultraviolet rays, X-rays, Gamma rays
94
What can ultraviolet waves do to the human body?
They can cause the skin to age prematurely and increase the risk of skin cancer.
95
What type of radiation are X-rays and gamma rays?
Ionising
96
How can X-rays and gamma rays damage cells?
They can damage cells by ionising atoms and, if absorbed by the nucleus, can cause gene mutations and cancer.
97
What is radiation dose?
Measured in Sieverts and is a measure of the risk of harm resulting from an exposure of body radiation.
1000 millisieverts = 1 Sievert (Sv)
98
How does a lens form an image?
By refracting light.
99
What are the two main types of lens?
Concave and convex
100
What does a convex lens look like?
It is wider in the middle than at the edges.
101
What does a convex lens do to rays of light?
Parallel rays of light entering a convex lens are brought to a focus at the principal focus/ focal point
102
Why are parallel rays of light entering a convex lens sometimes called converging lenses?
Because parallel rays of light entering a convex lens converge (come together), they are sometimes called converging lenses.
103
What is the focal length?
The distance from the lens to the principal focus.
104
What is a concave lens like?
A concave lens is wider at the edges than it is in the middle.
105
What happens to parallel rays of light that enter a concave lens?
Parallel rays of light entering a concave lens spread out. This makes the rays appear to have come form the principal focus on the same side of the lens that they originated, because parallel rays of light entering a concave lens diverge, they are sometimes called diverging lenses.
106
What is the principal axis?
It is the kind that goes through the centre of the lens at right angles to the lens surface.
107
What sort of images can convex lens produce?
Real or virtual images.
108
What sort of images can concave lenses produce?
Virtual images
109
What is a real image?
It is an image on the opposite side of the object and can be projected onto a screen.
110
What is a virtual image?
A virtual image is an image on the same side as the object and can only be seen by looking through a lens.
111
How do you draw ray diagrams?
- Draw the principal axis.
- Use the correct lens symbols
- Mark the principal foci on either side of the lens by drawing a dot on either side of the access and labelling it F
- Mark the position of the object as an arrow standing on the principal axis.
- Once diagram is drawn, draw light rays.
112
What is magnification?
The ratio of image height to object height
| E.g. a magnification of 2 means the image is twice the size of the object.
113
Why does magnification have no units?
It is a ratio
114
What does visible light describe?
Electromagnetic waves that can be detected by the human eye.
115
What can happen to light when it is incident (arrives at and hits) an object?
It can be absorbed, reflected or transmitted.
116
What is specular reflection?
Reflection by a smooth surface is a single direction (e.g. by a mirror)
117
What is diffuse reflection?
Reflection from a rough surface, where the light is scattered.
118
What are all objects?
Either transparent, translucent or opaque.
119
What does when an object is translucent mean?
They transmit light, but the rays are scattered so objects cannot be seen clearly through them e.g. frosted glass.
120
What does when an object is transparent mean?
The object transmits light coherently (the light rays do not get jumbled up) so objects on the other side can be seen clearly.
121
What does when an object is opaque mean?
They either defect or absorb all light incident on the so no light passes through them.
122
What does each colour within the visible spectrum have?
Its own narrow band of wavelength and frequency.
123
What does it mean when an opaque object appears coloured?
- It is reflecting light of that particular wave length.
| - it is absorbing other wavelengths
124
When does an object appear white?
If all wavelengths are reflected equally.
125
When does on object appear black?
If all wavelengths are absorbed.
126
How do coloured filters work?
By absorbing some wavelengths and not others.
127
What controls what colour the filter allows to pass through?
The wavelengths that are transmitted.
128
If the filter is the same colour as the object what colour will it appear?
Its true colour
129
What would happen if a red and blue striped object is seen through a red filter?
It would appear red and black because the filter will allow red light through but not blue light.
130
What would happen if we had a red object in green light?
The red object absorbed the green light, this light does not reflect any light and so appears black.
131
What will a red object look under magenta light?
Because magenta’s a mix of red and blue, a red object will appear red under magenta light.
132
How does temperature effect the amount of infrared radiation a body absorbs?
The horror the body the more infrared radiation it radiates in a given time.
133
What does the rate at which an object emits radiation depend on?
The nature of the surface and its temperature.
134
What is a perfect black body?
An object that absorbs all of the infrared radiation incident incident on it. It does not transmit any radiation. Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.
135
What does the temperature of a black body determine?
- The rate at which is emits radiation
| - The wavelength of the radiation it emits
136
What happens as the temperature of a black body increases?
As the temperature increases the amount of radiation an object emits at all wavelengths increases, but the intensity of shorter wavelengths increases faster.
137
What happens when an object is heated?
It first glows red hot. As it gets hotter, it emits even shorter wave lengths and becomes whiter.
138
What is the temperature of an object related to?
The balance between radiation absorbed and emitted.
139
Why will the temperature of the ground increase in temperature on a sunny day when the sun comes out?
This is because it absorbs radiation from the sun faster than it emits it. As the ground gets warmer the rate at which it emits radiation will increase. Eventually the rate of emission is equal to the rate of absorption and the ground will be at a constant temperature.
This applies to many other situations e.g. a radiator, a house, an object in front of a radiant heater and planet Earth.
140
What does the temperature of the Earth depend on?
- How much energy it receives from the sun.
- How much energy is reflected back into space.
- How much energy it emits into space.
141
What does the earth’s atmosphere also affect?
How much of the radiation emitted from the surface escapes into space.
