1
Q
What is the charge of a proton?
A
+1
2
Q
What is the relative mass of a proton?
A
1
3
Q
What is the charge of a neutron?
A
0
4
Q
What is the relative mass of a neutron?
A
1
5
Q
What is the charge of an electron?
A
-1
6
Q
What is the relative mass of an electron?
A
1/1835
7
Q
What is an isotope?
A
Atoms of the same element with the same number of protons but different number of neutrons
(Different mass numbers)
8
Q
How many element’s isotopes are stable?
A
Only one or two
9
Q
What is radioactive decay?
A
The unstable isotopes decay by emission of high energy particles or waves to become more stable
10
Q
What can electrons do if they gain enough energy?
A
Jump to a higher energy level (shell)
11
Q
Where do electrons get the energy from to jump to a higher energy level (shell)?
A
Electromagnetic radiation
12
Q
What happens soon after an electrons jumps to a higher energy level?
A
Fall back down to the lower energy level
13
Q
What will the electron re-emit when it falls back down to the lower energy level?
A
Re-emit the energy as electromagnetic radiation
14
Q
Loss of electron = …?
A
Positive ion
15
Q
Gain of electron = …?
A
Negative ion
16
Q
What does ionising radiation mean?
A
Able to knock electrons off atoms and so ionise them
17
Q
What is alpha made up of?
A
2 protons
2 neutrons
18
Q
What is the overall charge of an alpha particle?
A
2+
19
Q
Are alpha particles small or big?
A
Relatively large - easily stopped by collisions with other molecules
20
Q
How far can alpha penetrate?
A
Not very far:
A few cm in the air
Absorbed by a single sheet of paper
21
Q
Are alpha particles weak or strongly ionising?
A
Strongly ionising - easily knock electrons off of any atoms they collide with
22
Q
What are beta particles made up of?
A
Electrons
23
Q
What is the charge of beta particles?
A
-1
24
Q
Do beta particles have a mass?
A
No
25
How far can beta particles penetrate?
Far:
Several metres of air
5mm of aluminium or Perspex
26
Are beta particles weak or strongly ionising?
Weak/low ionising power
27
What are gamma rays?
Waves of electromagnetic radiation
(Pure energy)
28
When is gamma radiation often emitted?
After alpha or beta radiation
29
Why is gamma radiation often emitted after alpha or beta radiation?
A way of the nucleus getting rid of extra energy
30
Do gamma rays have a mass?
No
31
Do gamma rays have a charge?
No
32
How far can gamma rays penetrate?
Really far into materials:
Long distances through air
Thick sheet of lead or concrete needed to stop them
33
Are gamma rays weak or strongly ionising?
Very weak/low ionising power
34
What is background radiation?
The low-level ionising radiation in the environment which is always present
- radon gas
- ground + buildings
- medical
- food + drink
- cosmic rays
- nuclear power
35
What does a Geiger-Müller tube do?
Counts the number of particles/waves over a fixed time period
36
Equation for count rate
Number of counts
—————————
Time
37
What is the count rate measured in?
Becquerels, Bq
38
What 2 things can you use to detect radiation?
Geiger-Müller tube
Photographic film
39
What is the source of a beta particle?
A neutron decaying into a proton and an electron
40
What is activity?
The overall rate at which unstable nuclei decay
41
What is activity measured in?
Becquerels
42
1bq = …?
1 decay per second
43
The activity of a radioactive isotope …?
Decreases over time
44
Why does the activity of a radioactive source decrease over time?
As more unstable nuclei decay, the number of unstable nuclei decreases, so fewer decays happen per second
—> causes the activity to decrease over time
45
What does half-life mean?
1) the time taken for the activity or number of decays to halve
2) the time taken for the number of radioactive nuclei in a sample to half
46
Fewer radioactive nuclei = …?
A lower activity
47
What is irradiation?
The process by which objects are exposed to any type of radiation
48
What are the ionising radiations?
Alpha
Beta
Gamma
X-ray
49
What are the non-ionising radiations?
Ultraviolet
Microwave
50
What is contamination?
When radioactive particles get into other objects
51
What determines how harmful radiation is?
Type of radiation
Where your exposed to it (internally or externally)
The amount of radiation
52
What can radiation do to our DNA?
Ionise it which can cause mutations
53
What happens in rare cases if radiation mutates your DNA?
Lead to the cells dividing uncontrollably and develop cancer
54
What other type of radiation can also lead to cancer?
Ultraviolet
55
Most harmful radiation —> not harmful radiation (list)
Alpha
Beta
Gamma
X-rays
Ultraviolet
Visible light
Infra-red
Microwave
Radiowaves
56
What determines the amount of radiation you’re exposed to?
How far away from the source you are
How long you’re exposed to it
How radioactive that substance is
57
How can you minimise radiation (safety precautions)?
Wear protective gloves and overalls
Use long tongs
Wear goggle
Wear a dosimeter
Point away from body
Keep in a lead-lined box
Keep in a locked cupboard
58
How can radiation be used to detect a water leak?
1) the source of gamma radiation is put into the water and is being used as a tracer
2) a Geiger-Müller tube is used to locate the point where the radiation is the highest
3) where the water leaks into the ground, there will be more radiation given off
59
Which radiation is used for the thickness of kitchen foil?
Beta particles
60
Why are beta particles used for making the thickness of kitchen foil (aluminium)?
They can penetrate the foil but some particles will be absorbed
61
What does the number of beta particles that are absorbed depend on (aluminium)?
The thickness of the foil
62
What happens if the foil leaving the rollers is too thick?
Fewer beta particles will reach the detector and so the pressure on the rollers with be increased
63
What happens if the foil leaving the rollers is too thin?
More beta particles will reach the detector and so the pressure on the rollers will be reduced
64
What two ways is radiation used in medicine?
Radiotherapy
Medical tracers
65
What happens if our cells receive a large enough dose of radiation?
They can be killed off completely
—> radiation sickness
66
Where can radiotherapy be?
Internally or externally
67
Which radiation is used for external radiotherapy?
Gamma rays
68
How are gamma rays used in external radiotherapy?
They are targeted at the cancer site from lots of different angles so that only the cancer site gets the highest dosage
69
Which radiation is used for internal radiotherapy?
Beta
70
How is beta radiation used in internal radiotherapy?
Source is placed inside the body either inside or next to the cancer
71
What are the side effects of radiotherapy?
Healthy cells will also get damaged or killed
—> why cancer therapy often makes patients feel so ill
72
Where are medical tracers used?
Placing certain radioactive isotopes inside a person’s body by either injecting them or swallowing them
73
How do medical tracers work?
We can track the movement of the isotopes around the body by tracking the radiation they emit
74
How do we check to see if organs are working properly with medical tracers?
By seeing if they absorb the right amount of the substance
75
Which radiation is used for medical tracers?
Gamma rays
76
Why are gamma rays used for medical tracers?
They are less harmful than alpha and beta
77
Why do we want to use isotopes with as short half-life as possible?
So they only emit radiation for a short period while you take the measurements
—> then they stop being harmful
78
How can you minimise the risk of medical tracers?
Low dose
Short half-life
79
What is nuclear fission?
The splitting up of large unstable nuclei into smaller nuclei
80
What does fission release loads of?
Kinetic energy
81
How do we get all of our nuclear energy on Earth?
Nuclear fission
82
When can nuclear fission occur?
Spontaneously: fission is unforced and happens itself (rare)
Absorbing a neutron: which can split a nucleus by making it even less stable
83
What do we use to get the process of fission started in nuclear reactors?
Neutrons
84
What is a chain reaction?
The sequence of reactions produced when a nuclear fission reaction triggers one or more further fissions
85
What is alpha radiation used for?
Smoke detectors
86
What is beta radiation used for?
Monitor thickness of paper/aluminium
87
What is gamma radiation used for?
Sterilise surgical instruments
Preserve food
Detecting underground leaks
88
What health problems can be caused by radiation?
Mutations to DNA
Skin burns
Cancer
89
What happens if nuclear fission is not controlled properly?
The whole system can quickly get our of control
—> release huge amounts of energy
—> what happens in nuclear bombs
90
What controls the rate of fission in nuclear reactors?
Control rods
91
What is a control rod?
Lowered into the reactor to absorb neutrons to control the rate of reaction
92
What is the control rod made from?
Boron
93
What is a fuel rod?
Provides material for fission
94
What is a moderator?
Slows the neutrons down so they can be absorbed by the nuclei
E.g. heavy water
95
What is the moderator made from?
Graphite
96
What is shielding (nuclear reactors)?
Prevents irradiation of workers
97
Pros of nuclear reactors
Uranium and plutonium fuel is relatively cheap
Produces a large and steady amount of fuel
Not renewable energy but it is clean
Doesn’t produce green house gases like fossil fuels do
98
Cons of nuclear reactors
Nuclear power plants are very expensive to build
The nuclear waste they produce is expensive to get rid of
—> has to be buried underground in special bunkers
Always a risk of a major disaster if the plant malfunctions
—> very unlikely
—> but makes people suspicious of using nuclear energy
99
What is nuclear fusion?
When two lighter nuclei join/fuse to form a single larger nuclei
100
What does nuclear fusion release tons of?
Energy (more than nuclear fission)
101
In nuclear fusion what do the hydrogen nuclei form?
Helium
102
Is the helium atoms lighter or heavier than the two hydrogen nuclei?
Lighter
103
Why is the helium nuclei lighter than the two hydrogen nuclei?
Some of the mass is converted to energy
104
Why is so much energy released in nuclear fusion?
Some of the mass is converted to energy
105
What process fuels stars?
Nuclear fusion
106
How were all elements heavier than hydrogen made?
By nuclear fusion
107
What does nuclear fusion not produce?
Any radioactive waste
—> we can easily make the hydrogen that’s needed as fuel
108
What does fusion only occur in?
Really high temperatures and pressure
10,000,000 degrees celsius
109
Where does fusion occur?
Stars
110
Why can’t nuclear fusion be done on earth/why does it only happen at really high temperatures and pressure?
Fusion requires lots of energy for the two nuclei to fuse as they are both positively charged and so they repel
111
What does the unstable ‘parent’ nuclei split up into?
Two ‘daughter’ nuclei and two or three neutrons
112
What is the unstable nuclei called (pre fission)?
‘Parent’ nuclei
113
Why are gamma rays used to detect water leaks?
They are the most penetrating and so they can penetrate the ground
114
Why is alpha radiation used in smoke alarms?
It is the most ionising so it will ionise the air
115
If you’re irradiated what can’t you do?
Emit that radiation to others
116
If your contaminated what can you do?
Harm others
117
Which radiation is the most harmful inside your body?
Alpha
118
Why is alpha radiation the most harmful inside your body?
It is the most ionising
119
What is the most dangerous radiation outside the body?
Gamma
120
What do unstable nuclei undergo?
Radioactive decay
121
Radioactive decay is …?
Random and spontaneous
Physics
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