Waves, Electromagnetism and Space Flashcards
1
Q
What are waves used for?
A
To transfer energy and information
2
Q
What are transverse wave?
A
- waves that oscillate perpendicular to the direction of energy transfer
_/^_/^_/^_/^_
3
Q
Give an example of transverse waves
A
- ripples on the surface of water
- all electromagnetic waves
4
Q
What are longitudinal waves?
A
Waves that oscillate parallel to the direction of energy transfer
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
5
Q
Give an example of longitudinal waves
A
- sound waves in air
6
Q
What do mechanical waves need?
A
A medium to travel through
- can be transverse or longitudinal
7
Q
What is the amplitude of a wave?
A
The maximum displacement of a point on the wave from its un disturbed position
- height or depth of the wave crest from the center line
8
Q
What is the frequency of a wave?
A
The number of waves passing a point per second
9
Q
What is the wavelength of a wave?
A
The distance from a point on the wave to the equivalent point on the next wave
- peak to peak or trough to trough
10
Q
Where does refraction occur?
A
At a boundary between two differnent materials
- because the speed and wavelength change there
11
Q
What can happen to waves at a boundary between two materials?
A
They can be transmitted or absorbed
12
Q
What are sound waves?
A
Vibrations that travel through a substance
13
Q
Sound waves cannot travel through …
A
.. a vacuum
14
Q
How do you investigate waves?
A
- a ripple tank =water waves
- a stretched string = waves in a solid
- a signal generator/ loudspeaker = sound waves
15
Q
What increases the pitch of a note?
A
An increase in the frequency of the wave
16
Q
What changes the volume of a note?
A
LOUD = increased amplitude QUIET = decreased amplitude
17
Q
How do we hear sound?
A
Sound waves cause the ear drum to vibrate, which sends signals to the brain
18
Q
What are ultrasound waves?
A
Sound waves with a frequency above 20,000Hz
19
Q
Ultrasound waves are partly …
A
.. reflected at a boundary between two different types of body tissue
20
Q
Why are ultrasound scans safer than x-rays?
A
They are non-ionising
21
Q
What are seismic waves?
A
Waves that travel through the earth
22
Q
When are seismic waves produced?
A
In earthquakes where they spread out from the epicentre
23
Q
What type of waves are seismic waves?
A
Primary = longitudinal
/\/\/\/\/\/\/\/\
Secondary = transverse
_/^_/^_/^_/^_
24
Q
The earth is made up of …
A
- a liquid inner core
- a solid outer core
- the mantle
- the crust
25
The electromagnetic spectrum
| In order of decreasing wavelength and increasing frequency
```
Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet waves
Xrays
Gamma rays
```
26
How to remember the order of the electromagnetic spectrum:
```
Randy
Men
Inject
Viagra
Until
Xplosive
Growth
```
27
Electromagnetic waves transfer energy from a source to ...
.. an absorber
28
The human eye can only detect ...
.. visible light.
29
White light contains ...
.. all the colours of the visible light spectrum.
30
What is infrared radiation used for?
Carrying signals from remote control handsets and inside optical fibres.
31
What are microwaves used for?
Carrying satellite TV programmes and mobile phone calls
32
What are radio waves used for?
For radio and TV broadcasting, radio communications and mobile phone calls
33
How can electromagnetic radiation be hazardous?
- Microwaves and Radiowaves can heat the internal parts of people's bodies
- Infrared radiation can cause skin burns
- Ultraviolet waves can harm the skin and the eyes
- Xrays and Gamma rays damage living tissue when they pass through it
34
Further research needs to be done to see if ...
.. mobile phones are safe to use
35
What are carrier waves?
Waves that are used to carry information by varying their amplitude
36
What does the wavelength of radio waves affect?
- how far they travel
- how much they spread
- how much information they carry
37
What are optical fibres?
Very thin transparent fibres that are used to transmit communication signals by light and infrared radiation
38
What are Xrays used for?
To make xray images in hospitals
39
What are Gamma rays used for?
To kill harmful bacteria in food
To sterilise surgical equipment
To kill cancer cells
40
What does ionising radiation do to uncharged atoms?
Charge them
41
Where and why are Xrays used?
In hospitals to :
- make images of internal body parts
- destroy tumours at or near the body surface
42
What are Xrays absorbed by?
- More by bones and teeth
| - Less by soft tissue
43
What is the Normal?
A line drawn perpendicular to the mirror
44
What does the law of reflection state?
Angle of incidence = Angle of reflection
45
What is the angle of incidence?
The angle between the normal and the incident ray
46
What is the angle of reflection?
The angle between the normal and the reflection line
47
What is specular reflection?
Reflection in a single direction without scattering
48
What is diffuse reflection?
Reflection from a rough surface that scatters the light
49
What is refraction?
The change in direction of waves when they travel across a boundary from one medium to another
50
What happens to the angle of refraction when a light ray refracts as it travels into glass?
It is less than the angle of incidence
51
What happens to the angle of refraction when a light ray refracts as it travels from glass into air?
It is more than the angle of incidence
52
What happens to the wavelength of light across the visible spectrum?
It increases from red to violet
53
What does the colour of a surface depend on?
The pigments of the surface materials
| The wavelengths of light the pigments absorb
54
A translucent object lets light pass through it but ...
.. scatters or refracts the ligh inside it
55
A transparent object lets all the light that enters it pass through it and ...
.. does not scatter or refract the light inside the object
56
What does a convex lens focus?
Parallel rays to a point called to principle focus
57
What does a concave lens do?
Makes parallel rays spread out as if they had come from a point called the principle focus
58
When is a real image formed in a convex lens?
When the object is further away than the principle focus
59
When is a virtual image formed by a convex lens?
When the object is nearer than the principle focus
60
What can a rag diagram be drawn to find?
The position and nature of an image lens
61
Cameras contain convex lenses to form ...
.. real images of objects
62
A magnifying glass is a ...
.. convex lens that is used to form a virtual image of an object
63
Like poles ...
.. repel
64
Unlike poles ...
.. attract
65
Where do magnetic feild lines form around a bar magnet?
Curve around the bar from the north pole to the south pole
66
What is induced magnetism?
Magnetism created in an unmagnetised magnetic material when the material is placed in the magnetic field
67
Why is steel used instead of iron to make permanent magnets?
Steel doesn't lose its magnetism easily, whereas iron does
68
The magnetic field lines around a wire are ...
.. circles centred on the wire in a plane perpendicular to the wire
69
The magnetic field lines in a solenoid are ...
.. parallel to its axis and all travel in the same direction
70
What is a uniform magnetic field?
One where the magnetic field lines are parallel
71
What does increasing the current do to the magnetic field?
Makes it stronger
72
What happens to the magnetic field lines when you reverse the direction of the current?
They reverse their direction
73
What is an electromagnet?
A solenoid that has an iron core. It consists of an insulating wire wrapped around an iron bar.
74
Where are electomagnets used?
- scrapyard cranes
- circuit breakers
- electric bells
- relays
75
How do electromagnets work?
They attract an iron armature, which opens a switch
76
How is the force increased in the motor effect?
If the current or magnetic field strength of the conductor is increased
77
How is the force reversed in the motor effect?
If the direction of the current or the magnetic field is reversed
78
What is magnetic flux density?
A measure of the strength of a magnetic field
79
What is in an electric motor?
A coil that turns when the current is passed through it
80
What is the generator effect?
The effect of inducing a potential difference using a magnetic field
81
What happens when a conductor crosses through the lines of a magnetic field?
A potential difference is induced across the ends of the conductor
82
The direction of an induced current always opposes the ...
.. original change that caused it
83
What is a simple a.c. generator made up of?
A coil that spins in a uniform magnetic field
84
What is a simple d.c. generator made up of?
A split-ring commutator instead if two slip rings
85
What are transformers used for?
To increase or decrease the size of an alternating potential difference
86
The size of alternating potential difference is increased by ...
.. a step-up transformer.
87
The size of alternating potential difference is decreased by ...
.. a step-down transformer.
88
Why do transformers only work with an alternating current?
Because a changing magnetic field is necessary to induce a.c. in the secondary coil
89
What does a transformer have?
- a primary coil
- a secondary coil
- an iron core
90
How is a high grid potential difference made more efficient?
By reducing it to the current needed, therefore reducing power loss
91
How did the gas and dust clouds formed by the Solar System become more concentrated?
Gravitational attraction
92
What is a protostar?
A concentration of gas and dust that becomes hot enough to cause nuclear fussion
93
Why is energy released inside a star?
Because of hydrogen nuclei fusing together to form helium nuclei.
94
Why is the Sun stable?
Because gravitational forces acting inwards balance the forces of nuclear fusion energy in the core acting outwards.
95
When do stars become unstable?
When they have no more hydrogen nuclei that can fuse together.
96
Which stars have roughly the same mass as the Sun
- protostar
- main-sequence star
- red supergiant
- red giant
- white dwarf
- black dwarf
97
The Sun will eventually become a ...
.. black dwarf.
98
What is a supernova?
The explosion of a red supergiant after it collapses.
99
What keeps a planet moving along its orbit?
The force of gravity between a planet and the sun.
100
What keeps the satellite moving along its orbit?
The force of gravity between the Earth and a satellite.
101
Where is the force of gravity in an orbiting body in a circular orbit?
Towards the centre of thr circle.
102
What happens as a body in a circular orbit moves around the orbit?
- the magnitude of its velocity stays the same
- the direction of its velocity continually changes and is always at right angles to the direction of the force
- it experiences an acceleration towards the center of the circle
103
What must happen for a small body to stay in orbit at a particular point?
It must move at a particular speed around a larger body.
104
What is a red-shift of a distant galaxy?
The shift to longer wavelengths of the light from a galaxy because it is moving away from you.
105
The faster a galaxy is moving away from you, the ...
.. greater its red-shift is.
106
The further away a distant galaxy is from you, the ...
.. greater its red-shift is.
107
Why are distant galaxies moving from here?
Because the universe is expanding.
108
What created the universe?
The Big Bang.
- a massive explosion from a very small and extremely hot and dense region
- space, time and matter were created as a result
109
The universe has been expanding since ...
.. the Big Bang.
110
What is cosmic microwave background radiation?
Electromagnetic radiation that was created just after the Big Bang.
111
What evidence is there that the universe is expanding?
Red-shifts of the distant galaxies mean that they are moving further away.
