Section 3 - Radioactivity and Astronomy Flashcards
1
Q
What did JJ Thomson discover?
A
The atom has smaller bits
2
Q
How did JJ Thomson discover what he discovered?
A
The atom can lose an electron
3
Q
What did JJ Thomson suggest?
A
The ‘plum-pudding’ model
4
Q
What did Rutherford do?
A
Fired alpha particles at a thin gold foil
5
Q
What did Rutherford find following his experiment?
A
That most particles went straight through
Some were deflected more than they expected
Some were deflected back the way they had come
6
Q
What did Rutherford theorise based off his findings?
A
That the mass of the atom was concentrated in the center which was positive and most of the atom is empty space
7
Q
Whats part of our current model of the atom?
A
Protons and neutrons in the nucleus
Electrons in fixed orbits at set distances from the nucleus
8
Q
What is the relative mass of an electron?
A
0.0005
9
Q
Describe how the radius of an atom compares to the radius of its nucleus?
A
The radius of the atom is about 10,000 times bigger than the radius of the nucleus
10
Q
How do electrons move up to a higher energy level?
A
By absorbing EM radiation
11
Q
What will happen to an electron once it moves up a shell?
A
It will quickly fall back to its original energy level and in doing so will lose the same amount of energy it absorbed
12
Q
How is the energy carried away once an electron falls down an energy level?
A
EM radiation
13
Q
What determines the type of EM wave involved in electron levels?
A
The energy emitted
The higher the energy, the higher the frequency
14
Q
What is most often released when electrons move back to their original level?
A
Visible light
15
Q
Compare the energy difference from third - second and second - first electron level?
A
Third -> Second will release less energy, so a lower frequency wave than Second -> First
16
Q
As you move further out from the nucleus, the energy level get _________
A
As you move further out from the nucleus, the energy level get closer together
17
Q
As you move further out from the nucleus, the difference in energy gets ________
A
As you move further out from the nucleus, the difference in energy gets smaller
18
Q
What will happen to an electron if it absorbs too much radiation?
A
It will leave the atom
19
Q
What is ionising radiation?
A
Any radiation that can knock electrons from atoms
20
Q
What is a positive ion and how is one formed?
A
An atom with more protons than electrons
A positive ion is formed when an outer electron absorbs enough energy that it leaves the atom
21
Q
What are isotopes?
A
A type of an element with the same number of protons but a different number of neutrons
22
Q
How many elements have isotopes?
A
All of them
23
Q
How many stable isotopes are there usually per element?
A
One or two
24
Q
What happens to unstable isotopes?
A
They tend to decay into other elements and give out radiation
25
Why do unstable isotopes decay?
To attempt to become more stable
26
What do radioactive substances 'spit out'?
Gamma radiation
Alpha radiation
Beta radiation
Neutrons
27
What are alpha particles?
Helium nuclei (two protons and two nuetrons)
28
What is alpha radiation?
Alpha particles emitted from the nucleus of an atom
29
Describe how penetrative alpha radiation is?
Very weak
30
What stops alpha radiation?
A few cm of air
| Thin sheet of paper
31
Describe how ionising alpha radiation is?
Strongly ionising
32
What makes alpha radiation so ionising?
It's size
33
What can beta particles be?
Electrons or positrons
34
What is a beta-minus particle?
A fast moving electron released by the nucleus
35
What is a beta-plus particle?
A fast moving positron released from the nucleus
36
What is a positron?
The antiparticle of the electron
37
Describe the ionisingness of beta radiation?
Moderately ionising
38
Describe how ionising beta decay is?
Moderately ionising
39
What stops beta-minus decay?
Few meters of air
| Absorbed by a sheet of aluminium (5mm thick)
40
What stops beta-plus decay?
Electrons
41
Compare the range of beta-plus to beta-minus decay?
Beta-plus' range is much smaller
42
Why is the range of beta-minus much smaller?
Because when a positron hits an electron they destroy each other and produce gamma rays
43
What is annihilation?
The collision of a positron and an electron resulting in the destruction of both and the production of gamma rays
44
What happens to a nucleus once it has decayed?
It undergoes nuclear rearrangement and releases energy
45
Describe how penetrative gamma rays are?
Extremely
46
What stops gamma rays?
Thick sheets of lead
| Meters of concrete
47
Describe how ionising gamma radiation is?
Weakly ionising
48
Why are gamma rays so 'un-ionising'?
Because they tend to pass through rather than collide
49
For each of alpha, beta-minus and gamma radiations, give an example of a material that could be used to absorb it
Refer to the material's thickness in your answer
Alpha - A thin sheet of paper
Beta-minus - A 5mm thick sheet of aluminium
Gamma - A thick sheet of concrete or meters of concrete
50
What are nuclear equations of way of showing?
Radioactive decay
51
What is the golden rule of nuclear equations?
The total mass and atomic numbers must be equal on both sides
52
What does alpha decay do?
Decreases the charge by 2 and the mass by 4
53
What does beta-minus decay do?
Increases the atomic number by 1
54
What does beta-minus decay involve?
A neutron changing into a proton and an electron
55
What does beta-plus decay do?
Decreases the atomic number by 1
56
What does beta-plus decay involve?
A proton changing into a neutron and a positron
57
What does neutron emission do?
Decreases the mass number by 1
58
What does gamma radiation do?
Nothing
59
Why does gamma radiation do nothing?
Because its a way of getting rid of excess energy
60
What type of radiation is given off in this decay? 8 3 Li -> 8 4 Be?
Beta-minus
61
Write the nuclear equation for 219 86 Rn emitted an alpha particle?
219 86 Rn -> 215 84 Po + 4 2 α
62
What do radioactive sources contain?
Radioactive isotopes that give out radiation
63
How can you predict how many will have decayed in a given time?
By using the half-life of the source
64
What is the activity of a radioactive substance?
The rate at which a source decays
65
What is activity measured in?
Becquerels Bq
66
What is 1 Bq equal to?
1 decay per second
67
What measures activity?
A Geiger-Muller tube
68
What are methods of detecting radiation?
A Geiger-Muller tube
| Photographic film
69
How can you use a Geiger-Muller tube?
Count how many times it clicks
70
How can you use photographic film to measure radiation?
The more radiation the film's exposed to, the darker it becomes
71
What happens as the unstable nuclei all steadily disappear?
The activity as a whole will decrease
72
What is half-life?
The average time taken for the number of radioactive nuclei in an isotope to halve
73
What are the important parts of the half-life definiton?
Average for number of radioactive nuclei to halve
74
What does a short half-life mean?
The activity falls quickly
75
How dangerous are short half-life substances?
Very as there will be a high amount of radiation at the stary
76
What does a long half-life mean?
The activity falls slower
77
The activity of a radioactive sample is measured as 640 Bq
Two hours later it has fallen to 40 Bq
Find its half-life
```
640/2 = 320 1
320/2 = 160 2
160/2 = 80 3
80/2 = 40 4
```
Two hours / 4 = 30 minutes
78
What will a graph of activity against time be shaped like?
An inverse proportion graph
79
How do you find the half-life of a substance from a graph?
By finding the time interval on the bottom axis corresponding to a halving of the activity on the vertical axis
80
A radioactive source has a half-life of 60h and an activity of 480 Bq
Find its activity after 240h
240/60 = 4
```
480/2 = 240
240/2 = 120
120/2 = 60
60/2 = 30
```
81
What does background radiation come from?
```
Human activity
Cosmic rays
Foods
Buildings
Rocks
```
82
Where do most cosmic rays come from?
The Sun
83
What are examples of human activity that contribute to background radiation?
Fallout from nuclear explosions
| Nuclear waste
84
What is irradiation?
Exposure to radiation
85
How do you prevent irradiation?
Using lead-lined boxes
Standing behind barriers
Remote-controlled control
86
What do medical staff wear?
Photographic film badges to monitor their exposure
87
What does it mean when an object is contaminted?
Unwanted radioactive atoms have stuck onto an object
88
How could you prevent contamination?
Wearing gloves and protective suits
| Using tongs
89
How does radiation damage cells?
By ionisation
90
Describe how radiation damages cells by ionisation?
Radiation can enter living cells and ionise atoms and molecules within them
91
What can lower doses of radiation lead to?
Minor damage without killing the cells this can rise to mutant cells which divide uncontrollably (cancer)
92
What can higher doses of radiation lead to?
The death of cells which will cause radiation sickness if alot of cells all get blatted at once
93
What does radiation sickness lead to?
Vomitting
Tiredness
Hair loss
94
Outside the body, whats the most dangerous radiation?
Gamma and beta
95
Why are gamma and beta the most dangerous outside the body?
Because they can penetrate the body and get to the delicate organs
96
Inside the body, whats the most dangerous?
Alpha
97
Why is alpha the most dangerous inside the body?
Because alpha particles are strongly ionising so they do damage in a very localised area
98
What is the main worry with alpha sources?
| Contamination or irradiation?
Contamination
99
Give three sources of background radiation?
```
Any three from:
Fallout from nuclear explosions
Nuclear waste
Cosmic rays
Foods
Building materials
Rocks
```
100
What do the hazards associated with a radioactive source depend on?
It's half-life
101
The ____ the activity of a radioactive source, the safer it is to be around
The lower the activity of a radioactive source, the safer it is to be around
102
What must be considered when choosing a radioactive source for an application?
The activity of the source
The half life of the source
Disposal and storage of the source
103
What type of radiation is used for fire alarms?
Alpha
104
Where is the radiation placed, in the smoke alarm?
Between two electrodes
105
How do smoke alarms work?
The source of alpha radiation causes ionisation and a current of charged particles to flow meaning if there is a fire the smoke will absorb the charged particles meaning the current stops and the alarm sounds
106
Why is irradiation better than using high temperatures?
Because fresh fruit and plastic instruments can be sterilised without being damaged
107
What sources are used for tracers?
Beta or gamma
108
What can beta radiation be used in?
Thickness control
109
When measuring thickness control, why is beta radiation used?
Because the paper will partly block the radiation
110
Explain why radioactive sources that emit alpha radiation are not used as medical tracers?
Alpha radiation is highly ionising so would damage cells in the body. Alpha radiation can't penetrate through tissue, so it wouldn't be detected outside the body with the radiation detector
111
What can PET scanning help do?
Diagnose illnesses
112
What is PET scanning?
A technique used to show tissue or organ function and can be used to diagnose medical conditions
113
How can you detect cancer tumours?
By looking for high metabolic activity in tissue
114
Describe how you can undergo PET scanning?
Inject the patient with a substance used by the body containing a positron-emitting radioactive isotope
Positrons are emitted by the isotope which would meet electrons in an organ and annihilate which would emit high-energy gamma rays
Detectors outside the body then recieve the rays, undergoing triangulation to find the location of the source
115
What does the distribution of radioactivity equal?
The metabolic activity
116
Why does the metabolic activity = radioactivity?
Because the cells that have a higher metabolic rate will take in more gucose meaning there will be more gamma rays from that area
117
What are the isotopes used in PET scanning like?
Short half-lives
118
What makes isotopes?
Cyclotron
119
Because of the short half-lives what must hospitals do with the isotopes?
Use them quickly and make sure they're made close
120
What source is typically used when treating tumours?
Alpha
121
What source is typically used when treating implants?
Beta
122
What source can be used to treat tumours externally?
By aiming gamma rays at the tumour
123
Explain how a PET scan can detect a cancerous tumour in a patient?
The patient is injected with a substance that contains a radioactive isotopes
This isotope decays and produces positrons which annihilate with nearby electrons and produce gamma rays
These gamma rays are then detected outside of the body
Areas of high metabolism can indicate the presence of a cancerous tumour
124
What is nuclear fission?
The splitting up of an atoms nucleus
125
Briefly describe how to start nuclear fission?
A slow-moving neutron is fired at a large unstable nucleus which absorbs the neutron and causes the atom to become more unstable and eventually split
126
Once the atom splits, in nuclear fission, what happens next?
The atom splits to form two new lighter elements, energy and neutrons
127
What is produced once a Uranium-235 is split apart?
Two daughter cells
Neutrons
Energy
128
What element is often used in nuclear fission?
Uranium-235
129
What are thermal neutrons?
Slow-moving neutrons
130
What do control rods do in nuclear fission?
Limit the rate of fission by absorbing excess neutrons
131
What do moderators do in nuclear fission?
Limit the rate of fission by slowing down thermal neutrons
132
What could happen if the rate of fission is left unchecked?
Large amount of energy will be released in a very short time potentially resulting in an explosion
133
How do nuclear power stations get the energy from the fission?
The energy heats the coolant which is heated into steam which is then used to rotate a turbine which releases kinetic energy
134
What is nuclear fusion?
The joining of small nuclei
135
Briefly describe how nuclear fusion occurs?
Two light nuclei collide at high speed and join to create a larger, heavier nucleus
136
Compare the mass of the heavy nuclei to the two light nuclei?
The total mass of the light nuclei is slightly more as there is some mass converted to energy which is then released as radiation
137
What is the problem with fusion?
It requires extremely high temperature and pressure
138
What temperature is needed for fusion?
10,000,000 *C
139
Why are such high temperatures needed for nuclear fusion?
Because in order to join the nuclei you must overcome the strong force due to electrostatic repulsion as they are both positive
140
Why are the conditions for fusion so hard?
Because no material can withstand that kind of temperature as it would just be vapourised
141
Why are the no fusion reactors at the moment?
Because it takes more power to get up to the temperature than the reactor releases
142
What are the cons of nuclear power?
Bad public perception
Nuclear waste is hard to dispose of
Leaks (eg. Chernobyl and Fukushima)
143
What are the pros of nuclear power?
Pretty safe when done right
Very reliable
No greenhouse gases released
Fuel is cheap and readily available
144
Why is the cost of nuclear power so high?
Because of the inital cost of the power plant
145
Explain why fusion only occurs at high temperatures and pressures?
Because all nuclei have positive charges so when they are close they repel each other meaning high pressures/temperatures are needed to overcome this electrostatic repulsion and fuse the two nuclei together
146
What is solar system?
The stuff that orbits out Sun
147
What are planets?
Large objects that orbit a star
148
What are dwarf planets?
Planet-like objects that aren't big enough to be planets
149
What are moons?
Natural satellites that orbit planets with almost circular orbits
150
What type of orbits do moons have?
Almost circular
151
What type of orbits do artificial satellite have?
Fairly circular
152
What are asteroids?
Lumps of rock and meetals that orbit the Sun
153
What are comets?
Lumps of ice and dust that orbit the Sun.
154
What type of orbits do comets have?
Highly elliptical
155
What provides the force that creates orbits?
Gravity
156
What type of orbits do planets have?
Almost circular
157
Where does centripetal act?
Towards the centre of the circle
158
What affects graviational field strength?
The mass of the object
| The distance from the object
159
What must happen to the instantaneous velocity as the gravity increases?
The velocity must increase to balance it
160
What happens to an object the close it gets to a star or a planet?
The faster the object must go
161
For an object in a stable orbit, what must happen if the speed changes?
The radius of the orbit
162
What did the geocentric model involve?
The theory that the Sun, Moon, planets and stars all orbited the Earth in perfect circles
163
Why did the geocentric model arise?
Because we didn't have telescopes and saw the Sun andMoon travelling across the sky in the same way every day and night
164
What did the heliocentric model involve?
The theory that the Sun was at the centre of the solar system and that all the planets orbited the Sun in perfect circles
165
Who found evidence for the heliocentric model?
Galileo
166
What evidence did Galelio find for the heliocentric model?
There were 'stars' around Jupiter that never moved, meaning not everything orbited the Earth
These 'stars' are the moons of Jupiter
167
What is the difference between our current model of the solar system and the heliocentric model?
Orbits are elliptical rather than circular
| The Sun isn't the centre of the Universe
168
What does the Steady State theory say?
That as the Universe expands new matter is constantly being created meaning the density remains roughly the same because of this there is no beginning or end to the Universe
169
What does The Big Bang theory say?
All the matter in the Universe occupied a very small space which eventually 'exploded' causing space to expand
170
What does the Big Bang theory provide us with?
A start and an end
| An age of the universe
171
What is the estimated age of the universe?
13.8 billion years
172
What was the small space of all the matter in the Universe like?
Extremely dense and very hot
173
Explain the difference between the geocentric and heliocentric models of the Solar System?
In the geocentric model everything orbits the Earth, whilst, in the heliocentric model everything orbits the Sun
174
The Big Bang theory puts a finite age on the Universe, whereas, the Steady State theory assumes there is no beginning and no end to the Universe
In the Steady State Theory, matter is constantly being created. In the Big Bang theory, all of the matter in the Universe occupied a small, dense region of space at the start of the Universe, which then 'exploded' outwards
175
What does red-shift suggest?
The Universe is expanding
176
Different elements absorb ______ frequencies of light
Different elements absorb different frequencies of light
177
What do we see when we look at light from different galaxies?
We see the same patterns but at slightly lower frequencies meaning there's an observed increase in the wavelength of light coming from the galaxies
178
What is the red-shift but for sound?
Doppler effect
179
What happens to the sound of a car as it gets closer to you?
Higher pitched as the frequency increases
180
Compare more distant galaxies to closer galaxies in terms of red-shift?
Distant galaxies have greater red-shifts than closer galaxies
181
What does the distant galaxies and closer galaxies having different red-shifts show you?
That the whole universe is expanding
182
What is CMB radiation?
Low frequency electromagnetic radiation coming from all parts of the Universe
183
What is CMB evidence for?
The Big Bang
184
What is red-shift evidence for?
The Big Bang and Steady State
185
What is red-shift evidence for?
The Big Bang and Steady State
186
Why does red-shift only support the Big Bang theory?
Because it shows the Universe had a beginning
187
What is red-shift?
Red-shift is where the light we see from distant galaxies appears at a lower frequency than we would expect
188
What theory does CMB radiation support?
The Big Bang theory
189
State the cycle for a star bigger than the Sun?
```
Nebula
Protostar
Main Sequence Star
Red Supergiant
Supernova
Neutron Star or Black hole
```
190
State the cycle for a star the same size as the Sun?
```
Nebula
Protostar
Main Sequence Star
Red Giant
White Dwarf
```
191
What is a nebula?
A cloud of dust and gas
192
How is a protostar formed?
Dust and gas is pulled together to form a protostar
193
What happens to a protostar as it gets denser?
The temperature rises and more particles collide with each other meaning when the temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei which releases massive amounts of energy
194
What is thermal expansion of a star?
The energy produced by nuclear fusion trying to expand the star
195
What is the stable period of the star?
The main sequence star
196
What happens during the main sequence star stage?
The thermal expansion balances the force of gravity
197
The heavier the star, the _____ its time on the main sequence
The heavier the star, the shorter its time on the main sequence
198
What follows the main sequence star?
The supergiant
199
What happens after the main sequence star?
The hydrogen in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion
200
What happens once the force due to gravity is larger than the pressure of thermal expansion?
The star becomes compressed until it is dense and hot enough that the energy created makes the outer layers of the star expand
201
Why does the star become red?
The surface cools
202
What does a red giant turn into?
A white dwarf
203
How does a white dwarf form?
A small-to-medium-sized star like the Sun then becomes unstable and ejects its outer layer of dust and gas
204
What is a white dwarf?
A hot, dense solid core
205
What does a red supergiant turn into?
A supernova
206
What is a super nova?
An explosion
207
How does a super nova form?
A big star glowing brightly again as it undergoes more fusion to make heavier elements
They expand and contract several times as the balance shifts
208
What happens following a supernova?
A neutron star or a black hole
209
How is a neutron star formed?
The outer layer of dust and gas of a exploding supernova is thrown into space leaving a very dense core
210
How is a black hole formed?
If a star is massive enough it will collapse and become a black hole
211
What is a black hole?
A super dense point in space that not even light can escape
212
Describe the life cycle of a star much larger than our Sun, beginning from a nebula
A cloud of dust and gas is attracted together by gravity, forming a protostar
As the star gets denser, it gets hotter and hotter, until nuclear fusion of hydrogen nuclei starts to happen in its core
This nuclear fusion provides and outward pressure to balance the force of gravity, so the star remains a stable size, as a main sequence star
When the star runs out of hydrogen to fuse, it will expand and cool, becoming a red supergiant
It begins to glow brightly again and expands and contracts several times
213
What are optical telescopes?
Telescopes that detect light
214
What do telescopes use to allow you to see distant objects?
Refraction and reflection
215
How do you improve the quality of the image you can see through a telescope?
By increasing the aperature of the telescope
| By using a higher quality objective lens
216
What is the aperature of a telescope?
The diameter of the objective lens
217
Whats the problem with using telescopes on Earth?
The Earth's atmosphere absorbs light
| Light and air pollution
218
How could you avoid the problems with atmosphere and light pollution when using telescopes?
Ontop of a mountain
A dark place away from cities
In space
219
Whats the main problem with optical telescopes?
Most objects in the Universe aren't detectable using visible light
220
What are x-ray telescopes used to see?
Violent, high temperature events in space
221
What did radio telescopes help discover?
CMB radiation
222
What do computers allow us to do with telescopes?
Store huge amounts of data
Collect data 24 hours a day
No humans to rely on
Easier and quicker to analyse data
223
Give three ways of improving the image you can see through a telescope on Earth?
```
Any three from:
Move the telescope to a darker location
Move the telescope to a higher location
Move the telescope to space
Use a telescope with a larger aperture
Use a telescope with a higher quality objective lens
```
224
True or False? Atoms are neutral?
True
225
What is the atomic number of an atom?
The number of protons (and electrons) in an atom
226
Name four things that may be emitted during radioactive decay
```
Alpha
Beta-minus
Beta-plus
Gamma
Neutron
```
227
Explain why alpha radiation can not be used to check the thickness of metal sheets?
Because the alpha radiation wouldn't be able to penetrate the material
228
Describe the change to an atom's mass and atomic number following alpha decay?
The mass number decreases by 4. the atomic number decreases by 2.
229
In what type of decay does a neutron change into a proton within the nucleus?
Beta-minus
230
What type of nuclear decay doesn't change the mass or charge of the nucleus?
Gamma decay
231
Give three uses of radiation
PET scanning
Smoke sensors
Thickness control
232
What do asteroids orbit?
The Sun
233
What does CMB radiation stand for?
Cosmic Microwave Background radiation
234
List the life cycle stages a star the size of our Sun goes through?
```
Nebula
Protostar
Main Sequence Star
Red Giant
White Dwarf
```
