6. Waves Flashcards
1
Q
What type of wave is a sound wave?
A
Longitudinal
2
Q
Which type of vibrations move parallel to the direction of the wave?
A
Longitudinal
3
Q
Which type of vibrations move perpendicular to the direction of the wave?
A
Transverse
4
Q
Which waves can’t travel through a vacuum?
A
Mechanical
5
Q
Which waves can travel through a vacuum?
A
Electromagnetic
6
Q
Which waves pass their vibrations through particles?
A
Mechanical
7
Q
What is frequency measured in?
A
Hertz
8
Q
If one wave passes per second, what is the frequency?
A
1 Hz
9
Q
How do you work out frequency?
A
Frequency = 1 / Period
10
Q
What is a period?
A
How long is takes for the wave to pass a point - messed in seconds
11
Q
Equation for wave speed?
A
Wave speed = frequency x wavelength
12
Q
Equation for frequency?
A
Frequency = speed / wavelength
13
Q
Equation for wavelength?
A
Wavelength = speed / frequency
14
Q
What is the symbol for wavelength?
A
Lambda
15
Q
What does the angle of incidence equal?
A
The angle of reflection
16
Q
When light enters a glass cube, which direction does it refract?
A
Towards the normal
17
Q
What happens when light enters a denser glass block?
A
The speed of the wave decreases and it refracts towards the normal
18
Q
When the incident ray leaves the glass block, which direction does it go in?
A
Away from the normal
19
Q
What happens to the speed of the ray it leaves the glass block?
A
It speeds up and bends away from the normal
20
Q
What is the speed of a wave through a vacuum?
A
300,000,000 or 3x10 to the power of 8
21
Q
Do different electromagnetic waves carry different amount of energy?
A
Yes
22
Q
What happens when a ray is absorbed instead of reflected?
A
It heats up
23
Q
What happens as the energy of a wave increases?
A
The temperature and hazard increased
24
Q
What happens as the wavelength decreases?
A
The frequency increases The energy carried increases The waves become more dangerous The waves diffract less The waves have a shorter range The waves carry more information
25
What are the groups in the electromagnetic spectrum?
```
Gamma
X-ray
Ultraviolet
Visible
Infrared
Microwaves
Radio waves
```
26
What type of electromagnetic wave has the highest frequency and energy, and the shortest wavelength?
Gamma
27
What type of electromagnetic wave has the lowest frequency and energy, and the longest wavelength?
Radio waves
28
What are infrared waves used for?
To locate fire, detect humans and night vision
29
What type of wave is a light wave?
Transverse
30
What are radio waves used for?
Radio, TV, telecommunications
31
What are gamma waves used for?
Kills bacteria, radiotherapy, cancer treatment
32
What are microwaves used for?
Radar detection, satellite communications, cooking
33
What are in X-rays used for?
Examine damaged machinery and medical scans
34
What are visible waves used for?
Computers, TV, LED display, to see
35
What are ultraviolet waves used for?
Detect counterfeit banknotes
36
What are the hazards of infrared waves?
Overheating - burning
37
What are the hazards of radio waves?
None
38
What are the hazards of gamma waves?
Cancer mutations to tissue
39
What are the hazards of microwaves?
Damage parts of brain
40
What are the hazards of X-Ray's?
Body cells can be killed by high doses
41
What are the hazards of visible waves?
Intense beam damages eyes
42
What are the hazards of ultraviolet waves?
Sun burn, skin cancer
43
How are sounds made?
When an object vibrates and it causes the layer of air next to it to vibrate
44
Where do sounds travel fastest? Why?
Solids because the particles are closer together
45
Why is the no sound in a vacuum?
Because there are no particles to vibrate and pass on energy
46
What do you need to remember when doing f=v/lambda
MAKE SURE THAT THE WAVELENGTH IS IN METRES, THE TIME IN SECONDS AND FREQUENCY IN HZ
47
What is the range of normal human hearing?
20Hz to 20,000Hz
48
When will sound waves refract?
When air changes temperature (change in medium) - waves will travel slower in cooler air
49
Where does sound refract in the night?
Downwards, the air near the ground is cooler than the air higher up
50
What frequency are ultrasound waves?
Higher than 20,000Hz
51
When are ultrasound waves reflected?
When they reach a boundary between two different media
52
How do you determine how far away a boundary is?
How long the reflections take to reach the detector
53
What is ultrasound used for?
Medical
Industrial cleaning and no destructive testing of materials
54
Why does the ultrasound need to be a pulse?
So you can hear the echo
55
How is the time delay for an ultrasound and pulse worked out?
distance = speed x time
56
Why is gel used in ultrasound?
Because then there is more ultrasound absorbed. When there is a big difference between densities lots of it would be reflected.
57
What is the distance in ultrasound?
The way there and back
58
What is the depth in ultrasound?
Just the way there
59
Other uses of ultrasound?
The detection and removal of kidney stones
60
What makes seismic waves?
A sudden release of energy in the earths crust
61
What is used to detect movements of the earths crust?
A seismometer
62
What are the two types of seismic wave?
Primary and secondary
63
Properties of primary waves?
* longitudinal
* travels through solids and liquids
* travels faster
64
Properties of secondary waves?
* transverse
* only travel through solids
* travels slower
65
How does heat travel through space?
By infrared waves
66
What emits and absorbs thermal radiation?
All bodies
67
What is thermal (infrared) radiation?
The transfer of energy by electromagnetic waves
68
What is a thermograph?
The images taken using infrared radiation
69
What surface is the best emitter of infrared radiation?
Matte black surfaces
70
What surface is the worst emitter of infrared radiation?
Silver (shiny) surfaces
71
Best materials to emit infrared radiation? Best to worst
Matte black, shiny black, white, silver
72
Which kettle will cool down faster: black or metallic?
Black because it will emit more radiation
73
What direction does heat energy flow in?
From a hot object to a cooler one
74
What do good emitters also act as?
Good absorbers
75
What surface is the best absorber of infrared radiation?
Matte black surfaces
76
What surface is the worst absorber of infrared radiation?
Silver surfaces
77
Best materials to absorb infrared radiation? Best to worst
Matte black, shiny black, white, silver
78
Why are shiny surfaces the worst absorbers?
They reflect most of the radiation away
79
Why do solar panels have a black outer layer?
So it can absorb heat
80
Why are firefighters suits shiny?
They are the worst absorbers, the the best reflectors
81
Why is the back of a solar panel silver?
Reflect heat back onto pipes
82
Why are premature babies wrapped in silver blankets?
Its the worst emitter, so reduces the amount of heat that they lose
83
Why are radiators in car engines black?
It's the best emitter
84
What is a perfect black body?
An object that absorbs all the radiation that hits it
85
What does a perfect black body not do?
Reflect or transmit any radiation
86
What is the radiation emitted by a black body called?
Black body radiation
87
What is black body radiation?
The radiation emitted by a black body
88
If an object's temperature is higher, what will happen to the infrared radiation it's emitting?
Higher temperature -> more infrared radiation emitted in a given time
89
What happens as a filament lamp warms up?
* doesn't glow, emits infrared
* warms up glows dull red -> emitting visible spectrum
* orange-red
* yellow-white as filament gets hotter
90
What does the intensity of radiation at a certain wavelength depend on?
Temperature
91
What happens as temperature and radiation increases?
Radiation increases at every wavelength and the peak moves to a shorter wavelength (high frequency)
92
What happens to radiation as temperature increases?
If temperature increases, intensity of radiation increases at every wavelength so peak moves to a shorter wavelength
93
What does the temperature of the earth depend on?
1. The rate that light and infrared radiation are absorbed by the atmosphere/surface or are reflected back into space
2. The rate at which the earth emits radiation from its surface and atmosphere
94
Where does the sun's spectrum peak?
At visible wavelengths
95
What are the two major types of lens?
* concave
| * convex
96
What can concave lenses also be known as?
Diverging lenses
97
What can convex lenses also be known as?
Converging lenses
98
When is there a principal focus?
When the light rays are parallel
99
In a convex lens, how does the thickness of the lens affect the focal length?
The thicker the lens, the shorter the focal length
100
What is the shape of a converging lens?
It is thicker at the centre than the edges
101
What is the shape of a diverging lens?
It is thinner at the centre than the edges
102
How is magnification calculated?
magnification = image height / object height
103
If the image is larger than the object what is the magnification equal to?
greater than 1
104
If the image is smaller than the object what is the magnification equal to?
less than 1
105
What can the image in a convex lens be?
* real or virtual
* magnified or diminished
* upright or inverted
106
How is the image transformed in a camera?
(convex lens)
* diminished
* inverted
* real
107
How is the image transformed in a projector?
(convex lens)
* magnified
* inverted
* real
108
How is the image transformed in a magnifying glass?
(convex lens)
* magnified
* upright
* virtual
109
What type of images do convex lenses give?
* virtual
* upright
* diminished
110
What happens in a convex lens when the object moves further away from the lens?
The image gets smaller and moves away from the lens
111
How is short-sightedness corrected?
The eyeball is elongated so needs a concave lens
112
How is long-sightedness corrected?
Convex lens
113
Why does white light spread out into colours after it passes through a glass pyramid?
The different wavelengths experiences different changes in speed as they enter and leave the glass so refract by different amounts
114
Which colours are refracted the most and the least?
* red is refracted the least
| * violet is refracted the most
115
What are the primary colours of light?
Red, green, blue
116
What are the secondary colours of light?
Yellow, cyan, magenta
117
What does green and blue light create?
Cyan light
118
What does green and red light create?
Yellow light
119
What does green and red light create?
Magenta light
120
What does a filter do?
Only allows a small range of wavelengths to pass through
121
What does a red filter do?
Only allows red light through and absorbs blue and green light
122
What are opaque objects?
Those that do not transmit light
123
What does the colour that an objects appears depend on?
Which wavelengths are most strongly reflected
124
Why do objects appear white?
They reflect all of the wavelengths of visible light equally
125
Why does a red object look black through a blue filter?
A red object only reflects red light and the blue filter only transmits blue light, so only blue light shines on the red object and it is absorbed so it appears black
126
How is a light ray reflected by flat foil?
Reflected in a single direction (specular reflection)
127
How is a light ray reflected by crumpled foil?
Scattered (diffuse reflection)
