(Done) Waves (Paper 2) Flashcards
(94 cards)
1
Q
Describe the shape of a transverse wave
A
- The direction of oscillation is perpendicular to the direction of energy transferred by the wave
2
Q
Describe the shape of a longitudinal wave
A
- The direction of oscillation is parallel to the direction of energy transferred by the wave
3
Q
How do waves travel
A
- By transferring energy through a medium or a vacuum without transferring the particles in a medium
4
Q
How do longitudinal waves travel
A
- The vibrations of particles in the medium are parallel to the direction the wave travels, transferring energy through c ompressions and rarefactions
5
Q
What waves are transverse
A
- All electromagnetic waves e.g. light
- Waves in water
- Waves on a string
6
Q
What waves are longitudinal
A
- Sound waves in air, ultrasound
- Shockwaves e.g. some seismic waves
7
Q
What is the calculation relating wave speed, frequency and wave length
A
- Wave Speed = Frequency x Wave Length
8
Q
What three things can happen when waves arrive at a boundary between two different materials
A
- The waves are absorbed by the material the wave is trying to cross into (Energy enters the materials energy stores
- The waves are transmitted often leading to refraction
- The waves are reflected
9
Q
What rule should be followed for all reflected waves
A
- Angle of incidence = Angle of reflection
10
Q
What is the normal in context of reflection
A
- An imaginary line perpendicular to the surface at the point of incidence
11
Q
Define specular reflection
A
- When light is reflected in a single direction by a smooth surface e.g. a mirror
12
Q
Define diffuse reflection
A
- When a wave is reflected by a rough surface and the reflected rays are scattered in lots of directions
13
Q
Why does diffuse reflection occur
A
- The normal of each incoming ray is different due to the nature of a rough surface
14
Q
What happens when diffuse reflection occurs
A
- The surface appears matte (not shiny) and you do not get a clear reflection of objects
15
Q
Properties of all EM waves
A
- Transverse
- Travel at the same speed in air or a vacuum
16
Q
List the waves within the EM spectrum
A
- Radio waves
- Micro waves
- Infrared waves
- Visible light
- Ultra violet
- X-rays
- Gamma rays
17
Q
What is the wavelength of radio waves
A
- 1m - 10^4m
18
Q
What is the wavelength of micro waves
A
- 10^-2m
19
Q
What is the wavelength of infrared waves
A
- 10^-5m
20
Q
What is the wavelength of visible light
A
- 10^-7m
21
Q
What is the wavelength of ultra violet light
A
- 10^-8m
22
Q
What is the wavelength of x-rays
A
- 10^-10m
23
Q
What is the wavelength of gamma rays
A
- 10^-15m
24
Q
What happens as the wavelength in the EM spectrum decreases
A
- Frequency increases
25
Why is there a large range of frequencies in EM waves
- EM waves are generated by a variety of changes in atoms and their nuclei
26
What determines where a wave is refracted
- The change in speed of the wave when it crosses into the second material
27
Define refraction
- When a wave crosses a boundary between materials at an angle and changes direction
28
What happens when a wave crosses a boundary and slows down
- It will bend towards the normal
29
What happens when a wave crosses a boundary and speeds up
- It will bend away from the normal
30
What changes occur when a wave is refracted
- The wavelength changes however the frequency stays the same
31
What happens when a wave is refracted whilst travelling along the normal
- The wave changes speed but is not refracted
32
Define optical density
- The measure of how quickly light can travel through it
33
What are EM waves made up of
- Oscillating electric and magnetic fields
34
What are alternating currents made up of
- Oscillating charges
35
What is the relation between alternating current and electromagnetic waves
- The oscillating charges within alternating current produce oscillating electric and magnetic fields producing EM waves
36
What factors of an alternating current will be given to the wave it produces
- Frequency
37
How are radio waves produced
- Using an alternating current in an electrical circuit
38
How are radio waves transmitted and received
- The object in which charges (electrons) oscillate to create the radio waves is called a transmitter
- When transmitted radio waves reach receiver, the radio waves are absorbed
- The energy carried by the waves is transferred to the electrons in the receiver
- This energy causes the electrons to oscillate and, if the receiver is part of a complete electrical circuit, it generates an alternating current
39
Define long-wave radio
- Waves with wavelengths between 1 and 10 km
40
How is long-wave radio transmitted around the world
- Long wavelengths diffract (bend) around the curved surface of the earth
- Long wavelengths can also diffract around hills and into tunnels
41
Define short-wave radio signals
- Radio waves with a wavelength of about 10m-100m
42
Define the ionosphere
- An electrically charged layer in the Earth's upper atmosphere
43
How is short-wave radio transmitted around the world
- Short-wave radio is reflected from the ionosphere
44
Applications of short-wave radio
- Bluetooth
45
What conditions determine whether medium-wave signals can reflect off the ionosphere
- Atmospheric conditions
- Time of day
46
What are microwaves used for
- Microwave ovens
- Communication to and from satellites
47
Why are microwaves used to communicate with satellites
- They can pass easily through earth's watery atmosphere
48
How do microwaves communicate with satelites
- Signal from a transmitter is transmitted into space
- Signal is picked up by the satellite receiver dish
- Satellite transmits the signal back to earth in a different location
- Signal is picked up by a satellite dish on the ground
49
How are microwaves used in microwave ovens
- Microwaves are absorbed by water molecules in the food
- Microwaves penetrate a few centimetres in the food being absorbed and transferring energy to the water molecules in the food causing the water to heat up
- The water molecules then transfer this energy to the rest of the molecules in the food by heating which quickly cooks the food
50
What is a use of infrared radiation
- To increase or monitor temperatures
51
How does infrared radiation occur
- Infrared radiation is given out by all hot objects - the hotter the object, the more radiation it gives out
52
How is infrared radiation used to monitor temperature
- Infrared cameras detect the radiation and turn it into an electrical signal which is displayed on a screen as a picture
- The hotter the object is, the brighter the image appears
53
How is infrared radiation used to increase temperature
- Absorbing infrared radiation causes objects to get hotter
54
What is a practical use of visible light
- Transmitting data via fibre optic cables
55
How is visible light used to transfer data via fibre optic cables
- Optical fibres can carry data over long distances vial pulses of visible light
- Light is reflected back and forth within the cables until they reach the end of the fibre
56
What is a use of ultraviolet light
- Fluorescent lights
57
How is ultraviolet light used for fluorescent lights
- Fluorescent chemicals emit visible light when ultra violet radiation is absorbed
- Fluorescent lights generate UV radiation, which is absorbed and re-emitted as visible light by a layer phosphor on the inside of the bulb
58
What are the practical uses of X-rays
- To take X-ray photographs
- To treat cancer
59
How are X-rays used to take X-ray photographs
- X-rays pass easily through soft tissue such as flesh however struggles to pass through denser material such as bone
- The plate of an X-ray begins white and becomes black, this is a negative image
- The white parts of the photo are where less X-rays got through therefore are the parts where X-rays where stopped by bones
60
How are X-rays and gamma rays used to treat cancer
- High doses of X-rays and gamma rays kill all living cells so are carefully directed to the cancer to treat it
61
What are the practical uses of gamma rays
- As a medical tracer
- To treat cancer
62
How are gamma rays used as medical tracers
- A gamma-emitting source is injected into a patient
- Its progress is followed around the body
- Gamma radiation is well suited for this because it can pass out of the body to be detected
63
What are the effects of each type of EM radiation based on
- How much energy the wave transfers
64
Damage caused by low frequency waves
- Don't transfer much energy
- Mostly pass through soft tissue without being absorbed
65
Damage cause by high frequency waves
- Transfer lots of energy, possibly ionising
- Can cause gene mutation or cell destruction and cancer
66
Damage caused by UV radiation
- Damage surface cells
- Sunburn, skin ages prematurely
- Blindness, increased risk of skin cancer
67
What is radiation dose measured in
- Sieverts (Sv)
68
Name the two types of lens
- Concave
- Convex
69
Describe the shape of a concave and convex lens
- Concave bends inwards
- Convex bends outwards
70
What do concave and convex lenses do to light parallel to the axis
- Concave causes light to diverge from the principal focus
- Convex causes light to converge towards the principal focus
71
Define principal focus for concave and convex lenses
- For concave lenses, the principal focus is the point where rays hitting the lens parallel to the axis appear to all come from
- For convex lenses, the principal focus is where rays hitting the lens parallel to the axis all meet
72
Define focal length
- The distance from the centre of the lens to the principal focus
73
State the two rules for refraction in convex lenses
- An incident ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
- An incident ray passing through the principal focus refracts through the lens and travels parallel to the axis
74
State the two rules for refraction in concave lenses
- 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
75
Define a real image
- Where the light from an object comes together to form an image on a 'screen'
76
Define virtual image
- When the rays are diverging so the light from an object appears to be coming from a completely different place
77
Three features which are needed to describe an image properly
- How big it is compared to the original object
- Whether it is upright or inverted
- Whether it is real or virtual
78
Features of an image produced from a concave lens
- Virtual image
- The right way up
- Smaller
- Same side of the lens as the object
79
What does colour and transparency of an object depend on
- Absorbed wavelengths
80
What causes objects to be opaque
- Light is not transmitted
- They absorb some light wavelengths and reflect the ones we see
81
What causes objects to be transparent or translucent
- Some or all light is transmitted through the object
82
Function of primary colour filters
- Only allows light of that colour to pass through the filter
- If that colour of light is not present, the object appears black
83
What properties are better than others at absorbing and emitting radiation
- Black is better that white
- Matt is better than shiny
84
Define a perfect black body
- An object that absorbs all the radiation that hits it
85
Properties of a perfect black body
- Best possible emitter of EM radiation
86
What is he overall temperature of the earth dependant on
- The amount of radiation it reflects, absorbs and emits
87
How do we hear sounds
- Sound waves that reach your ear drums can cause it to vibrate
- These vibrations are passed on through tiny bones in your ear called ossicles, through the semi-circular canals and to the cochlea
- The cochlea turns these vibrations into electrical signals which get sent to your brain which allow you to sense sound
88
State the human hearing range
- 20Hz - 20kHz
89
What factors limit the human hearing range
- Size and shape of the ear drum
- The structure of all the parts in the ear that vibrate to transfer energy from the sound wave
90
Define ultrasound
- Sound with frequencies higher than 20kHz
91
What is a practical use of Ultrasound
- Detecting how far away something is and developing an image from that
- E.g. medical imaging, industrial imaging
92
How is ultrasound used to find distance
- Ultrasound waves are partially reflected at wave boundaries
- Waves travel at fixed speeds in a medium
- The distance between the start point and the surface can be calculated by using the time taken for the ultrasound wave to return
93
Features of S waves
- Transverse
- Can only travel through solids
- Slower than P waves
94
Features of P waves
- Longitudinal
- Can travel through solids and liquids
