Topic 6 waves GCSE Physics Flashcards
(117 cards)
1
Q
What happens when waves travel through a medium?
A
- the particles of the medium oscillate and transfer energy between each other
2
Q
What is the amplitude of a wave?
A
- maximum displacement of a wave from its undisturbed position
3
Q
What is the wavelength?
A
- distance between the same point of two adjacent waves (between the trough of one wave and the trough of another)
4
Q
What is the frequency?
A
- number of complete waves passing a certain point per second
- measured in Hz
5
Q
What can you find from the frequency?
A
- period of the wave
- so the amount of time it takes for a full cycle of the wave
6
Q
How can you calculate the period of a wave?
A
period= 1/frequency
7
Q
How are the vibrations in transverse waves?
A
- oscillations are perpendicular to the direction of energy transfer
8
Q
What are some examples of transverse waves?
A
- all electromagnetic waves (light)
- ripples and waves in water
- a wave on a string
9
Q
How are the vibrations in longitudinal waves?
A
- oscillations are parallel to the direction of energy transfer
10
Q
What are some examples of longitudinal waves?
A
- sound waves in air (ultrasound)
- shock waves
11
Q
What is wave speed?
A
- the speed at which energy is being transferred
12
Q
What is the wave equation?
A
wave speed= frequency X wavelength
13
Q
How can you use an oscilloscope to measure the speed of sound? - p24
A
1-set up the oscilloscope so the detected waves at each microphone are shown as separate waves
2- start with both microphones next to the speaker, then slowly move one away until the two waves are aligned on the display (but have moved exactly one wavelength apart)
3- measure the distance between the microphone to find one wavelength
4- then use the formula wave speed = wavelength X frequency to find the speed
14
Q
What is the speed of sound in air?
A
- 330 m/s
15
Q
How can you measure the speed of water ripples using a lamp? p74
A
1- using a signal generator attached to the dipper of a ripple tank
2- use a lamp to see wave crests on a screen below the tank
3- the distance between each shadow line is equal to one wavelength, measure the distance between the shadow lines that are 10 wavelengths apart
4- use wave speed = frequency X wavelength to measure speed of waves
16
Q
How can you use the wave equation for waves on a string?
A
p74 look at diagram
17
Q
What are the three things that can happen when waves arrive at a boundary between two materials?
A
1- waves are absorbed by the material, this transfers energy to the materials energy store
2- the waves are transmitted, carry on travelling to new material
3- waves are reflected
18
Q
What is the rule of all reflected waves?
A
angle of incidence = angle of reflection
19
Q
What is the angle of incidence?
A
- angle between the incoming wave and the normal
20
Q
What is the angle of reflection?
A
- angle between the reflected wave and the normal
21
Q
What is the normal?
A
- imaginary line that’s perpendicular to the surface at the point of incidence
- shown with a dotted line
22
Q
When does speculation reflection happen?
A
- happens when a wave is reflected in a single direction by a smooth surface
23
Q
What is diffuse reflection?
A
- happens when a wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions
24
Q
Why does diffuse reflection happen?
A
- because the normal is different for each incoming ray which means the angle of incidence is different for each ray
25
What are all EM waves?
- transverse waves that transfer energy from a source to an absorber
26
What do all EM waves travel at?
- same speed through air or a vacuum
27
What do electromagnetic waves form?
- a continuous spectrum over a range of frequencies
28
How are electromagnetic waves grouped?
- into 7 different types
- based on their wavelength and frequency
29
What is the order of the electromagnetic spectrum from smallest to highest?
radio, micro, infrared, visible light, ultra violet, X-rays, gamma rays
30
Why is there such a large range of frequencies for the EM spectrum?
- because EM waves are generated by a variety of changes in atoms and their nuclei
31
What happens when a wave crosses a boundary between materials at an angle?
- the wave changes direction
- so its refracted
32
What does refraction in waves depend on?
- depends on how much the wave speeds up or slows down
- usually depends on the density of the two materials
33
What happens if a wave crosses a boundary and slows down or speeds up?
slows down- it will bend towards the normal
speeds up- bend away from the normal
34
What is the optical density of a material?
- measure of how quickly light can travel through it (bottom of pg 76 for ray)
35
How can you use transparent materials to investigate refraction?
1- place a transparent rectangular block on a piece of paper and trace around it, use a ray box or laser to shine a ray in the middle of one side of the box
2- trace the incident ray and mark where the light ray emerges
3- remove block and draw a straight line, join the incident ray and the emerging point to show the path of the refracted ray
4- draw normal where the light ray entered the block
5- measure the angle
36
How can you find out the amount of light that different materials reflect?
1- draw a straight line on a piece of paper
2- shine a ray of light at the objects surface and trace the incoming reflected light beam
3- draw a normal where the light hits the object
4- measure angle of incidence and angle of reflection
5- repeat experiment with different objects
37
What are EM waves made up of?
- oscillating electric and magnetic fields
38
What are alternating currents made up of?
- oscillating charges
- as the charges oscillate, they produce oscillating electric and magnetic fields (electromagnetic waves)
39
How can you produce radio waves?
- using an alternating current in an electrical circuit
40
What is a transmitter?
- object which changes oscillate to create the radio waves is called a transmitter
41
What happens when transmitted radio waves reach a receiver?
- they are absorbed
- energy carried by the waves is transferred to the electrons in the material of the receiver
- energy causes electrons to oscillate
- if receiver id part of a complete electrical circuit it generates an alternating current
42
What are radio waves?
- used mainly for communication
- EM radiation with wavelengths no longer than 10cm
43
Why can short-wave radio signals be received at long distances from the transmitter?
- at long distances from the transmitter
- because they are reflected from the ionosphere
44
What does Bluetooth use?
- short wave radio to send data over short distances between devices without wires
45
What can medium waves signals can reflect?
- reflect from the ionosphere depending on the atmospheric conditions and the time of day
46
What are radio waves used for?
- TV and FM radio transmissions (have very short wavelengths)
47
Why can long-wave radio wavelengths be transmitted halfway around the world?
- long wavelengths diffract (bend) around the curved surface of the Earth
48
What do communications to form satellites use?
- microwaves
49
In microwave ovens how are the microwaves absorbed?
- by water molecules in food
50
How does water heat up in a microwave?
- the microwaves penetrate up to a few centimetres into the food before being absorbed and transferred the energy they are carrying to the water molecules in the food
- causing the water to heat up
- the water molecules transfer this energy to the rest of the molecules in the food by heating
- which quickly cooks the food
51
What can infrared cameras be used to detect?
- used to detect infrared radiation and monitor temperature
- detects IR radiation and turns it into electrical signal which is displayed on a screen as a picture
- the hotter the object the brighter it appears
52
What does absorbing IR radiation cause?
- objects to get hotter
- food can be cooked using IR radiation
- the temperature of the food increases when it absorbs IR radiation
53
How do electric heaters work?
- contain a long piece of wire that heats up when a current flows through it
- the wire emits lots of infrared radiation
- the emitted IR radiation is absorbed by objects and the air in the room
- energy is transferred by the IR waves to the thermal energy stores of the objects causing the temperature to increase
54
What are optical fibres?
- thin glass or plastic fibres that can carry data over long distances as pulses of visible light
55
How do optical fibres work?
- because of reflection
- the light rays are bounced back and forth until they reach the end of the fibre
56
When is visible light used?
- in optical fibres
57
Why is light not easily absorbed or scattered?
- as it travels along a fibre
58
What is fluorescence?
- property of certain chemicals where ultra violet radiation is absorbed and then visible light is emitted
59
What do fluorescent lights generate?
- UV radiation
- which is absorbed and re emitted as visible light by a layer of a compound called a phosphor on the inside of the bulb
- energy efficient so used in classrooms
60
When are security pens used?
- to mark property with your name
- under UV light the ink will glow but its invisible otherwise
- this can help police identify your property if stolen
61
When is ultraviolet radiation produced?
- produced by the sun
- exposure to it is what gives people a suntan
62
What is used in tanning salons?
- UV lamps are used
- over exposure can be dangerous
63
When are radiographers used in medicine?
- hospitals to take X-ray photographs of people to see if they have broken bones
64
What can X-rays pass through?
- easily through flesh but not so easy through denser materials like bones and metals
65
What do radiographers use X-rays and gamma rays for?
- to treat people with cancer
- high doses of these rays kill all living cells so they are carefully directed towards cancer cells to avoid killing to many normal healthy cells
66
How can gamma radiation be used as a medical tracer?
- a gamma emitting source is injected into the patient
- its progress is followed around the body
- gamma radiation is well suited to this because it can pass out through the body to be detected
67
What do radiographers do when there is X-rays and gamma rays that are harmful?
- wear lead aprons and stand behind a lead screen or leave the room
68
How much energy do low frequency waves transfer?
- radio waves
- don't transfer much energy so mostly pass through soft tissue without being absorbed
69
What do high frequency waves transfer?
- UV, gamma rays
- all transfer lots of energy and so can cause lots of damage
70
Which type of radiation are X-rays and gamma rays?
- ionising radiation
71
What can UV radiation damage?
- surface cells
- leading to sunburn and cause skin to age prematurely
- blindness and skin cancer
72
How are UV radiation, X-rays, gamma rays be useful?
- the risk of a person involved in a car accident developing cancer from having X-ray photograph taken is much smaller than the potential health risks of not finding and treating their injures
73
What is radiation dose a measure of?
- measured in sieverts
- measure of the risk of harm from the body being exposed to radiation
74
What does a CT scan use?
- X-Rays and a computer to build up a picture of the inside of a patients body
75
How do lenses form images?
- by refracting light and changing its direction
76
What is a convex lens?
- bulges outwards
- causes rays of light parallel to the axis to be brought together (converge) at the principal focus
77
What is a concave lens?
- caves inwards
- causes parallel rays of light to spread out
78
What is the axis of a lens?
- a line passing through the middle of the lens
79
What is the principal focus of a convex lens?
- where rays hitting the lens parallel to the axis all meet
80
What is the principal focus of a concave lens?
- where rays hitting the lens parallel to the axis appear to all come from
81
What is the focal length?
- the distance from the centre of the lens to the principal focus
82
What are the three rules for refraction in a convex lens?
- an incident ray parallel to the axis refracts through the lens and passes through the principle focus on the other side
- an incident ray passing through the principial focus refracts through the lens and travels parallel to the axis
- an incident ray passing through the centre of the lens carries on in the same direction
83
What are the three rules for refraction in a concave lens?
- an incident ray parallel to the axis refracts through the lens and travels in line with the principal focus
- an incident ray passing through the lens towards the principal focus refracts through the lens and travels parallel to the axis
- an incident ray passing through the centre of the lens carries on in the same direction
84
What is a real image?
- where the light from an object comes together to form an image on a screen
85
What is a virtual image?
- when the rays are diverging so the light from the object appears to be coming from a completely different place
86
What are the three things to describe an image?
1- how big it is compared to the object
2- whether its upright or inverted relative to the object
3- whether its real or virtual
- ray diagram draw learn p83 for concave and convex
87
What does a concave lens produce?
- virtual image
88
How do you find magnification produced by a lens at a given distance?
magnification= image height/object height
89
How do magnifying glasses work?
- by creating a magnified virtual image
90
Do opaque objects transmit light?
- do not transmit light
- when visible light waves hit them they absorb some wavelengths of light and reflect others
91
What does the colour of an opaque object depend on?
- which wavelengths of light are most strongly reflected
92
What do opaque objects that aren't a primary colour reflect?
- either the wavelengths of light corresponding to that colour or the wavelengths of the primary colours that mix together to make that colour
93
What do white objects reflect?
- reflect all of the wavelengths of visible light equally
94
What do black objects absorb?
- absorbs all of the wavelengths of visible light
95
What do transparent and translucent objects transmit?
- transmit light
- not all light that hits the surface of the object passes through, some is absorbed or reflected
96
What are coloured filters are used for?
- filter out different wavelengths of light so only certain colours are transmitted
- the rest are absorbed
97
What does a primary colour filter transmit?
- that colour
- so if a white light is shone at a blue coloured filter only blue light would be let through
- the rest are absorbed
98
What happens if you look at a blue object through a blue colour filter?
- it would still look blue
- blue light is reflected from the objects surface and is transmitted by the filter
99
What happens if you looked at a red object through a blue coloured filter?
- the object would appear black
- all of the light reflected by the object will be absorbed by the filter
100
What colours are filters mainly used for?
- filters that aren't for primary colours let through both the wavelengths of light for that colour and the wavelengths of the primary colours that can be added together to make that colour
101
excluding 86 and 87
dont know if i have learnt
102
What are sound waves caused by?
- vibrating objects
- these vibrations are passed through the surrounding medium as a series of compressions and rarefactions
103
How does sound travel?
- faster in solids
- than liquids
- and faster in liquids than in gases
104
How does a sound wave travel through a solid?
- it causes the particles in the solid to vibrate
105
Why cant sound travel in space?
- because its mostly a vacuum
106
How can you hear sound when your ear drum vibrates? p88
1- sound waves that reach your ear drum can cause it to vibrate
2- these vibrations are passed on to tiny bones in your ear called ossicles through the semi-circular canals and to the cochlea
3- the cochlea turns vibrations into electrical signals which get sent to your brain (allow you to sense)
- different materials can convert different frequencies of sound waves into vibrations
107
How will sound waves be reflected?
- by hard flat surfaces
- echo's are just reflected sound waves
108
Do sound waves refract?
- refract as they enter different media
- as they enter denser materials they speed up because when a wave travels in a different medium, its wavelength changes but its frequency remains the same
109
How does ultrasound ger reflected at boundary's?
1- when a wave passes from one medium into another, some of the wave is reflected off the boundary between the two media, some is transmitted
2- so you can point a pulse of ultrasound at an object and wherever there are boundaries between one substance and another some of the ultra sound gets reflected back
3- the time it takes for the reflections to reach a detector can be used to measure how far away the boundary is
110
How is ultra sound used in medical imaging?
- ultrasound eaves can pass through the body but whenever they reach a boundary between two different media some of the wave is reflected back and detected
- the exact timing and distribution of these echo's are processed by a computer to produce a video image of the foetus
111
How is ultrasound used in industrial imaging?
- ultrasound can be used to find flaws in objects such as pipes or materials such as wool or metal
- ultrasound entering a material will usually be reflected by the far side of the material
112
What can happen when a wave arrives at a boundary between two materials?
- can be completely reflected or partially reflected
113
What does an earthquake produce?
- seismic waves which travel out through the earth
114
What happens when seismic waves reach a boundary between different layers of material?
- some of the waves will be absorbed and some will be refracted
115
What are the two types of seismic waves?
- P waves
- S waves
116
What are P waves inside the earth?
- P waves are longitudinal
- they travel through solids and liquids
- they travel faster than S-waves
117
What are S-waves inside the earth?
- transverse and cant travel through liquids or gases
- they are slower than P-waves
