radioactivity Flashcards
1
Q
What are atoms considered to be?
A
The building blocks of all matter
2
Q
What is located at the center of an atom?
A
nucleus
3
Q
What particles orbit around the nucleus of an atom?
A
Electrons
4
Q
What is the relative atomic mass of protons?
A
One unit
5
Q
What particles are found in the nucleus of an atom?
A
- Protons
- Neutrons
6
Q
What is the charge of a neutron?
A
No charge
7
Q
What is the total charge in an atom?
A
Zero
8
Q
What happens when an atom loses electrons?
A
It is said to be ionised
9
Q
What does nuclear notation describe?
A
Particular nuclei by their element symbol, atomic number, and mass number
10
Q
What is the atomic number of an element?
A
The number of protons in an atom
11
Q
Why is the atomic number important?
A
It determines which element an atom is
12
Q
What is the mass number of an atom?
A
The total number of particles (protons and neutrons) in the nucleus
13
Q
How can the number of neutrons be calculated?
A
Mass number - atomic number
14
Q
What is an isotope?
A
An atom of the same element with an equal number of protons but a different number of neutrons
15
Q
What is an example of an unstable isotope of carbon?
A
Carbon-14
16
Q
What are the three types of radiation emitted from unstable nuclei?
A
- Alpha (α) particles
- Beta (β) particles
- Gamma (γ) radiation
17
Q
What is radioactive decay?
A
The process by which unstable nuclei emit radiation to become more stable
18
Q
What is the nature of alpha particles?
A
They are the same as a helium nucleus
19
Q
What are beta particles?
A
High-energy electrons produced when a neutron changes into a proton and an electron
20
Q
What type of radiation has the highest energy?
A
Gamma rays
21
Q
What is the penetrating power of alpha radiation?
A
Stopped by paper
22
Q
What is the penetrating power of beta radiation?
A
Stopped by a few millimeters of aluminum
23
Q
What is the penetrating power of gamma radiation?
A
Partially stopped by thick lead
24
Q
What is the purpose of the Geiger-Muller tube in radiation experiments?
A
To measure the count rate of a radioactive source
25
Fill in the blank: The total number of protons and neutrons in an atom is called its _______.
Mass number
26
True or False: The mass number is equal to the number of protons plus the number of electrons.
False
27
What must be equal for an atom to have no overall charge?
The number of protons and electrons
28
What is the purpose of taking readings with absorbers in radiation experiments?
To determine the type of radiation emitted by a source based on the reduction in count rate
29
What type of radiation is indicated if the count rate reduces when paper is present?
Alpha radiation
30
What does it suggest if the count rate reduces with a few mm of aluminium present?
Beta radiation
31
If some radiation can penetrate a few mm of lead, what type of radiation is being emitted?
Gamma radiation
32
What should be ensured to avoid systematic errors during radiation experiments?
Sources must be stored away from the counter and experiments should be conducted in the same location
33
What can improve the accuracy of radiation experiments?
Using reliable sources with a long half-life and activity above natural background levels
34
What is a key safety consideration when handling radioactive sources?
Use tweezers or tongs and keep a distance from the source
35
What does the acronym SCREAMS stand for in the context of conducting experiments?
* S: Same variable kept constant
* C: Variable changed
* R: Reliability measures
* E: Equipment and equations used
* A: Result analysis
* M: Measured variable
* S: Safety precautions
36
What happens during alpha decay?
An alpha particle is emitted, forming a new element and decreasing both mass and atomic numbers
37
What is an alpha particle composed of?
2 protons and 2 neutrons
38
In alpha decay, how are the mass number and atomic number affected?
Mass number decreases by 4 and atomic number decreases by 2
39
What occurs during beta decay?
A neutron changes into a proton and an electron, emitting the electron
40
How does beta decay affect the mass number and atomic number?
Mass number remains the same; atomic number increases by 1
41
What is emitted during gamma decay?
A gamma ray
42
How does gamma decay affect the atomic and mass numbers?
Neither the mass number nor the atomic number changes
43
What is neutron emission?
A process where a nucleus emits a neutron, decreasing the mass number by 1 without changing the atomic number
44
How is a decay equation structured?
It shows particles before the decay on the left and particles produced after the decay on the right
45
What is background radiation?
The radiation that exists around us all the time from natural sources
46
Name two natural sources of background radiation.
* Radon gas
* Cosmic rays from space
47
What are artificial sources of background radiation?
* Nuclear medicine
* Nuclear waste
* Nuclear fallout
* Nuclear accidents
48
How can background radiation be accounted for in laboratory readings?
By measuring the count rate with no radioactive source and subtracting it from the total count rate
49
What does a Geiger-Müller tube measure?
Radiation by counting decays and transmitting pulses to a counting machine
50
What happens to photographic film when it absorbs radiation?
It becomes darker upon development
51
What is the significance of the corrected count rate?
It provides an accurate measurement of radiation by accounting for background radiation
52
Fill in the blank: The atomic number decreases by _____ during alpha decay.
2
53
Fill in the blank: During beta decay, the atomic number increases by _____
1
54
True or False: Gamma decay results in a change in the mass number of the nucleus.
False
55
What is the corrected count rate?
The count rate measured with a radioactive source present, minus the background count rate
## Footnote
This calculation helps isolate the radiation from the source being studied.
56
How can the background count rate be measured?
Using a Geiger-Müller (GM) tube with no source present
## Footnote
This provides a baseline measurement of radiation in the environment.
57
If a Geiger counter records 24 counts in 1 minute without a source, what is the background radiation count rate in counts per second?
0.4 counts per second (cps)
## Footnote
Calculation: 24 counts per minute / 60 seconds = 0.4 cps.
58
What is the formula to find the corrected count rate when a source is present?
Count rate of the source - Background count rate
## Footnote
This helps in determining the actual radiation from the source.
59
What would be the corrected count rate if a Geiger counter records 285 counts in 1 minute with a source present and the background count is 24?
261 counts per minute (cpm)
## Footnote
Calculation: 285 - 24 = 261 cpm.
60
How can the accuracy of count rate measurements be improved?
* Repeating readings and taking averages
* Taking readings over a long period of time
## Footnote
These methods help mitigate random errors and fluctuations.
61
What is the background radiation count when the source is moved back far enough that it is all absorbed by the air?
15 counts per minute
## Footnote
This is the amount of radiation detected solely from background sources.
62
What are the significant natural sources of background radiation?
* Radon gas from rocks and buildings
* Food and drink
* Cosmic rays
## Footnote
These sources contribute substantially to the background radiation levels.
63
True or False: The background radiation is the amount of radiation received only when a radioactive source is present.
False
## Footnote
Background radiation is always present, regardless of radioactive sources.
64
What are objects containing radioactive nuclei called?
Sources of radiation
65
How is the activity of a radioactive source defined?
The rate at which the unstable nuclei decay
66
In what unit is activity measured?
Becquerels (Bq)
67
What does 1 Becquerel represent?
1 nucleus in the source decaying in 1 second
68
How does activity vary with time for a radioactive source?
The activity decreases with time
69
What is the process of radioactive decay?
A random process
70
What device is used to measure the count rate of a radioactive source?
Geiger-Muller (GM) tube
71
What is the activity of a source if it is 2000 Bq?
2000 nuclei decay every second
72
What is half-life?
The time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half
73
Can the half-life of different isotopes vary?
Yes, it can vary from a fraction of a second to billions of years
74
What is the half-life of uranium-235?
704 million years
75
What is the half-life of carbon-14?
5700 years
76
What happens to the amount of a radioactive isotope after each half-life?
The amount remaining decreases by half
77
How can half-life be calculated using a graph?
By measuring the time it takes for the activity to decrease to half its original value
78
What is the activity of a radioactive sample that drops from 880 Bq to 220 Bq?
2 half-lives have passed
79
What is the half-life of a sample if it drops to 220 Bq in 1 year?
3 months
80
What are some uses of radioactivity?
* Smoke detectors
* Monitoring the thickness of materials
* Medical procedures
* Sterilising food
* Determining the age of ancient artefacts
81
What type of radiation is used in smoke detectors?
Alpha particles
82
Why are beta particles used to measure the thickness of materials?
They are partially absorbed by the material
83
What is radiotherapy?
The treatment of cancer using radiation
84
What is a tracer in medical terms?
A radioactive isotope used to track the movement of substances in the body
85
What does irradiation mean?
The process of exposing a material to ionising radiation
86
What is contamination?
The accidental transfer of a radioactive substance onto or into a material
87
What is the risk of contamination?
It is particularly dangerous if a radioactive source gets inside the human body
88
How can exposure to radiation be minimized?
* Using shielding
* Wearing protective clothing
* Limiting time of exposure
89
Which type of radiation is most dangerous inside the body?
Alpha sources
90
Which type of radiation is the most penetrating?
Gamma sources
91
What is the difference between irradiation and contamination?
* Irradiation: Exposure to radiation without becoming radioactive
* Contamination: Becomes radioactive due to radioactive material
92
How does the risk of irradiation differ between short and long half-lives?
Irradiation poses a greater risk with shorter half-lives
93
How does the risk of contamination differ between short and long half-lives?
Contamination poses a greater risk with longer half-lives
94
What can ionising radiation cause to living cells?
Damage to DNA and mutations that can lead to cancer
95
What practices can be followed to minimize the risks of contamination?
Keeping radioactive sources in a shielded container, wearing gloves, using tongs, wearing protective clothing, limiting exposure time.
## Footnote
For example, a lead-lined box can be used to store radioactive sources safely.
96
How can the risks of irradiation to workers be minimized?
By monitoring their exposure to radiation.
## Footnote
This includes measuring the dose received during different activities.
97
What is a dosemeter?
A device that measures the amount of radiation in particular areas and is often worn by radiographers.
## Footnote
It is also referred to as a radiation badge.
98
How should alpha-emitting nuclear waste be stored?
In plastic or metal canisters.
99
What is the storage requirement for beta-emitting nuclear waste?
It must be stored inside metal canisters and concrete silos.
100
How should gamma-emitting nuclear waste be stored?
In lead-lined, thick concrete silos.
101
Why must radioactive waste be stored securely for a long time?
Because it emits dangerous levels of radiation for many years.
102
Where should waste with the highest levels of radioactivity typically be buried?
In secure, geologically stable locations underground.
103
What are the characteristics of containers used for radioactive waste disposal?
They must be strong, resistant to rust and corrosion, and able to withstand harsh conditions.
104
What should be ensured about the disposal site for radioactive waste?
It must have high security and a low risk of natural disasters.
105
What is one method to minimize the concentration of radioactive materials in waste?
Diluting it in large volumes of seawater.
106
Fill in the blank: A student should keep the gamma source in a _______ until it is needed.
lead lined container
107
What should a student use to move a gamma source instead of handling it directly?
Tongs.
108
What should be recorded after using a gamma source?
The date and the time that the radiation has been used.
109
True or False: The time that the source is being used should be maximized.
False.
110
List four actions a student should take to minimize risks when using a gamma source.
* Keep the source in a lead lined container until needed
* Use tongs to move the source
* Keep the source as far from themselves as possible
* Minimize the time the source is used
111
What is nuclear energy?
The energy contained in the nucleus of an atom, which can be harnessed for power.
112
What is nuclear fusion?
The process when two small nuclei join together to produce a larger nucleus.
113
Where does nuclear fusion occur naturally?
In stars.
114
What isotopes of hydrogen are involved in fusion reactions on Earth?
Deuterium and tritium.
115
What is the energy equivalent of 1 kg of hydrogen undergoing fusion?
Equivalent to burning about 10 million kilograms of coal.
116
What is nuclear fission?
The process when one large nucleus splits into two smaller nuclei.
117
What is a parent nucleus in the context of nuclear fission?
The large nucleus that splits during fission.
118
What are daughter nuclei?
The smaller nuclei produced from the fission of a parent nucleus.
119
What is spontaneous fission?
Fission that occurs without additional energy being put into the nucleus.
120
What is induced fission?
Fission that occurs when an unstable nucleus absorbs a neutron.
121
What is the half-life of uranium-235?
700 million years.
122
What happens during the fission of uranium-235?
It absorbs a neutron, becomes uranium-236, and then splits into smaller nuclei and neutrons.
123
What is critical mass?
The minimum amount of fissile material required to maintain a chain reaction.
124
What are control rods used for in a nuclear reactor?
To absorb neutrons and control the rate of fission.
125
What is the purpose of a moderator in a nuclear reactor?
To slow down neutrons.
126
What materials are commonly used for shielding in a nuclear reactor?
Steel and concrete.
127
What is the main difference between fusion and fission?
Fusion involves nuclei joining together, while fission involves nuclei splitting apart.
128
What are the conditions required for nuclear fusion?
Extremely high temperatures and pressures.
129
What is a major advantage of fusion reactors over fission reactors?
Fusion produces no long-lived nuclear waste products.
130
What is a disadvantage of fusion reactors?
The conditions for nuclear fusion are much harder to achieve and maintain on Earth.
131
Which isotopes of hydrogen are used in fusion reactions in stars?
Deuterium and tritium.
132
What is thermal equilibrium in the context of nuclear reactors?
When neutrons are slowed down to react efficiently with the uranium fuel.
133
Fill in the blank: Nuclear fission reactions produce _______ nuclei that are usually unstable and radioactive.
smaller daughter
134
True or False: Nuclear fusion is currently a commercially viable method for generating electricity.
False.
135
What happens to the mass during fusion reactions?
A small amount of mass is converted into energy.
136
What is the purpose of shielding in a nuclear reactor?
To absorb hazardous radiation.
137
What type of neutrons are required to induce fission?
Thermal neutrons.
138
Fill in the blank: The process of nuclear fusion requires _______ to maintain the reaction.
extremely high temperatures
139
What is the significance of hydrogen in stars?
It is the fuel for nuclear fusion that produces energy.
140
What are the products of fission when a uranium-235 nucleus splits?
Two smaller daughter nuclei, two or three neutrons, and gamma rays.
