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Radioactivity Flashcards

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1
Q

What are the main particles that make up an atom?

A

Protons, neutrons, and electrons

Protons and neutrons are found in the nucleus, while electrons orbit the nucleus.

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2
Q

What is the atomic number of an atom?

A

The number of protons in the atom

The atomic number also equals the number of electrons in a neutral atom.

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3
Q

What does the mass number of an atom represent?

A

The total number of protons and neutrons

It does not include electrons.

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4
Q

Define isotopes.

A

Atoms of the same element with the same number of protons but different numbers of neutrons

Isotopes can have different physical properties.

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5
Q

What is background radiation?

A

Nuclear radiation that we are exposed to all the time

It is emitted by natural and artificial sources.

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6
Q

List some sources of background ionising radiation.

A
  • Radon gas from igneous rocks
  • Radioactive substances in food and air
  • Building materials like granite
  • Artificial sources like medical treatments and nuclear waste
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7
Q

What is cosmic background radiation?

A

Radiation that comes from the sun

It is a component of background radiation.

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8
Q

What is ionising radiation?

A

Radiation strong enough to remove an electron from an atom

It can be dangerous to living organisms.

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9
Q

What are the three types of ionising radiation?

A
  • Alpha particles
  • Beta particles
  • Gamma rays
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10
Q

Describe an alpha particle.

A

Consists of two protons and two neutrons

It is strongly ionising but not very penetrating.

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11
Q

Describe a beta particle.

A

A high-speed electron

It is moderately ionising and more penetrating than alpha particles.

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12
Q

What are gamma rays?

A

Very high frequency electromagnetic waves

They are produced when an unstable nucleus loses energy.

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13
Q

True or False: Alpha particles are highly penetrating.

A

False

Alpha particles are not very penetrating.

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14
Q

Fill in the blank: The atomic number is equal to the number of _______.

A

Protons

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15
Q

Fill in the blank: Isotopes have the same number of protons but different numbers of _______.

A

Neutrons

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16
Q

Properties of alpha particle?

A

Strongly ionising and so not very penetrating.

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17
Q

Properties of beta particle?

A

Moderately ionising and more penetrating than alpha.

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18
Q

Properties of gamma rays?

A

They are weakly ionising and very penetrating.

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19
Q

When are gamma rays produced?

A

When an unstable nucleus loses energy.

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20
Q

What stops an alpha source?

A

A few sheets of paper.

Alpha particles are relatively large and can be stopped by light materials.

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21
Q

What stops a beta source?

A

A few millimetres of aluminium.

Beta particles are lighter than alpha particles and require denser materials for shielding.

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22
Q

What stops gamma rays?

A

A few centimetres of lead.

Gamma rays are highly penetrating and require substantial density to be effectively stopped.

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23
Q

Which type of radiation is the most penetrating?

A

Gamma rays.

Due to their lack of charge and high energy, gamma rays are the least easily stopped.

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24
Q

What equipment can detect all three types of radiation?

A

Geiger-Muller detector.

This device can detect ionising radiation, including alpha, beta, and gamma radiation.

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25
Q

What must you remember to do when measuring radiation with a Geiger-Muller detector?

A

Subtract the background radiation.

This is done by measuring the count rate with the source removed.

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26
Q

In a magnetic field, how are alpha and beta particles deflected?

A

In opposite directions.

This occurs due to their opposite charges.

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27
Q

Why are alpha particles deflected less than beta particles?

A

Alpha particles have a larger mass.

Their greater mass means they are less affected by magnetic fields.

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28
Q

How are gamma rays affected by magnetic fields?

A

They are not deflected.

Gamma rays are uncharged and thus unaffected by magnetic fields.

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29
Q

In an electric field, how do alpha and beta particles behave?

A

They are deflected in opposite directions.

This deflection is due to their opposite charges.

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30
Q

Why do alpha particles experience less deflection in electric fields compared to beta particles?

A

Due to their much larger mass.

Heavier particles are less responsive to electric forces.

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31
Q

What happens to gamma rays in electric fields?

A

They aren’t deflected.

Gamma rays, being uncharged, do not interact with electric fields.

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32
Q

What occurs when a radioactive isotope decays?

A

Its nucleus changes from an unstable to a more stable state and gives out energy as ionising radiation

Decay is a random process.

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33
Q

What types of decay result in a change of atomic number?

A

Alpha and beta radiation

Gamma decay does not change the atomic number.

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34
Q

What happens during alpha decay?

A

An alpha particle (helium nucleus) is emitted, consisting of two protons and two neutrons, resulting in the atomic number decreasing by 2 and the mass number decreasing by 4

Example: 238/92 U -> 234/90 Th + 4/2 He.

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35
Q

What is emitted during beta decay?

A

An electron is ejected when a neutron in the nucleus changes into a proton

The atomic number increases by 1 while the mass number remains the same.

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36
Q

What is the effect of gamma decay on atomic and mass numbers?

A

The mass and atomic number stay the same

This occurs as particles in the nucleus rearrange to a more stable position by releasing excess energy.

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37
Q

Fill in the blank: In alpha decay, the atomic number goes down by _______.

A

2

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38
Q

Fill in the blank: In alpha decay, the mass number goes down by _______.

A

4

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39
Q

True or False: Gamma decay results in a change of atomic number.

A

False

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40
Q

What is the outcome of a neutron changing into a proton during beta decay?

A

The atomic number increases by 1 while the mass number stays the same.

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41
Q

What does an alpha particle consist of?

A

Two protons and two neutrons

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42
Q

Example of a nuclear equation for alpha decay?

A

238/92 U -> 234/90 Th + 4/2 He

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43
Q

What rearranges during gamma decay?

A

Particles in the nucleus

44
Q

What type of radiation is emitted during gamma decay?

A

Gamma rays

45
Q

What is half-life in the context of radioactivity?

A

The time taken for the activity of a radioactive source to decrease to half the initial value or the time it takes for half of the nuclei of the isotope to decay into another isotope.

46
Q

How is the activity of a radioactive source measured?

A

In Becquerels (Bq).

47
Q

What happens to the activity of a radioactive source after n half-lives?

A

It equals 1 / 2° of the original value of activity.

48
Q

What is radiocarbon dating?

A

A method that estimates the age of organic material by measuring the amount of radioactive carbon-14 it contains.

49
Q

What is the half-life of carbon-14?

A

About 5600 years.

50
Q

How do living organisms contain carbon-14?

A

Plants absorb carbon-14 during photosynthesis, and animals consume plants and each other.

51
Q

What happens to carbon-14 levels when an organism dies?

A

The proportion of carbon-14 decreases as it decays.

52
Q

What are the limitations of radiocarbon dating?

A

Only works with organic material, destroys the sample, assumes constant carbon-14 proportion, requires a reasonable amount of material, and is only accurate up to around 10 half-lives.

53
Q

What is the purpose of radiotherapy?

A

To target cancer cells with radiation emitted from outside the body to kill or reduce tumor size.

54
Q

What characteristics should radiation have for effective radiotherapy?

A
  • Long half-life
  • Gamma radiation to penetrate the body
  • Non-toxic as it does not enter the body.
55
Q

What are medical tracers used for?

A

To check if all organs are working properly by showing where a tiny amount is absorbed.

56
Q

What characteristics should medical tracers have?

A
  • Short half-life
  • Gamma radiation to be picked up from outside the body
  • Non-toxic as it enters the body.
57
Q

What is used to trace underground leaks in pipes?

A

A radioactive tracer can be added to a fluid e.g. gas

The leak is indicated by an increased count rate in that area.

58
Q

What type of radiation is used for sterilisation?

A

Ionising radiation

Strong sources can kill micro-organisms, used on medical instruments and food.

59
Q

What does automatic thickness monitoring depend on?

A

The amount of radiation received by the detector

This allows adjustments to the thickness of materials like aluminium.

60
Q

How do smoke detectors function?

A

An alpha emitter ionises an air gap

Smoke absorption of alpha particles drops current, triggering the alarm.

61
Q

What type of radiation can penetrate the skin and damage cells?

A

Beta and gamma radiation

They can damage tissues and organs if they penetrate the skin.

62
Q

Which type of radiation is very dangerous if it gets inside the body?

A

Alpha radiation

It cannot penetrate the skin but can be harmful when internal.

63
Q

What happens when radiation collides with molecules in cells?

A

Causes ionisation, damaging or destroying molecules

This can lead to cell mutations and cancer.

64
Q

What is the effect of lower doses of radiation?

A

Tends to cause minor damage without killing the cell

This can potentially lead to mutations and cancer.

65
Q

Fill in the blank: A _______ tracer can be used to trace underground leaks.

A

radioactive

The tracer is non-toxic and has a short half-life.

66
Q

True or False: Gamma radiation is used for sterilisation because it has a long half-life.

A

True

Long half-life is beneficial for sterilisation processes.

67
Q

What is the purpose of using alpha radiation in smoke detectors?

A

To ionise an air gap and conduct electricity

This allows the detector to sense smoke by a drop in current.

68
Q

What type of radiation is typically used in automatic thickness monitoring?

A

Beta radiation

It is used for monitoring the thickness of materials like aluminium.

69
Q

What is radiation sickness?

A

A condition caused by high levels of radiation exposure that can kill cells completely.

70
Q

How is low-level radioactive waste typically disposed of?

A

By burying it in landfill sites.

71
Q

What is the primary challenge in disposing of high-level radioactive waste?

A

It is hard to get rid of and is often sealed in glass blocks and buried deep underground.

72
Q

What factors must be considered when finding a suitable place for high-level waste disposal?

A

Must not be in an earthquake-prone area to prevent leakage and contamination.

73
Q

What is contamination in the context of radioactivity?

A

When unwanted radioactive atoms get onto or into an object.

74
Q

What is a potential consequence of contamination?

A

Contaminated atoms may decay, releasing radiation and causing harm.

75
Q

What safety measures should be taken when handling radioactive sources?

A

Use gloves and tongs to prevent contamination.

76
Q

What is irradiation?

A

The exposure of objects near a radioactive source without making them radioactive.

77
Q

What are some methods to reduce the risk of irradiation?

A
  • Keeping sources in lead-lined boxes
  • Standing behind barriers
  • Using remote controls
78
Q

What is nuclear fission?

A

A nuclear reaction that can be a source of energy, involving the splitting of a fissile material.

79
Q

What is the most commonly used fissile material?

A

Uranium-235.

80
Q

What are the products of a nuclear fission reaction?

A
  • Two daughter nuclei (fission fragments)
  • Neutrons
  • Gamma radiation
  • Kinetic energy
81
Q

What initiates the process of nuclear fission?

A

A collision with a slow-moving neutron

This collision leads to the absorption of the neutron by Uranium-235.

82
Q

What unstable isotope is formed when Uranium-235 absorbs a neutron?

A

Uranium-236

83
Q

What is produced when Uranium-236 splits apart during fission?

A

Two daughter nuclei and additional neutrons

84
Q

What is a chain reaction in the context of nuclear fission?

A

A process where the fission of one nucleus causes further fissions in other nuclei

85
Q

Fill in the blank: The fission of uranium-235 can be initiated by a _______.

A

slow-moving neutron

86
Q

What are the components of a nuclear power station?

A

Control rods, boiler, steam, turbine, generator, condenser, nuclear reactor

87
Q

What material are moveable control rods typically made of?

A

Boron

88
Q

What effect do control rods have when moved down between fuel rods?

A

They absorb neutrons and slow the rate of reaction

89
Q

What happens to uranium fuel rods during fission?

A

They become very hot and radioactive

90
Q

What is the purpose of adjusting the depth of control rods in a nuclear reactor?

A

To maintain a constant rate of fission

91
Q

True or False: The coolant in a nuclear reactor is always hot.

A

False

92
Q

What type of core is commonly used in a nuclear reactor?

A

Graphite core

93
Q

What structure encases the reactor vessel in a nuclear power station?

A

Concrete shield

94
Q

Fill in the blank: The coolant enters the reactor vessel _______.

A

cold

95
Q

What is the primary function of the generator in a nuclear power station?

A

To produce electricity

96
Q

What is the function of the moderator in a nuclear reactor?

A

Surrounds fuel rods and slows down neutrons to increase absorption likelihood

This process kickstarts nuclear fission.

97
Q

What role does the coolant play in a nuclear reactor?

A

Transfers thermal heat energy from fuel rods to the heat exchanger

An example of a coolant is water.

98
Q

How does the heat exchanger work in a nuclear reactor?

A

Converts water into high pressure steam using heat energy from the coolant

This steam turns the turbine, which generates electricity.

99
Q

What is the purpose of the concrete shield in a nuclear reactor?

A

Absorbs radiation such as high energy neutrons and gamma rays

This protects against ionising radiation emitted from the reactor.

100
Q

Define nuclear fusion.

A

The joining of two atomic nuclei to form a larger one

This process releases energy.

101
Q

What is the mass comparison of the larger nucleus formed in nuclear fusion?

A

The larger nucleus has a smaller mass than the combined masses of the two smaller nuclei

Energy is released during this process.

102
Q

What element undergoes fusion in stars to create helium?

A

Hydrogen nuclei

This process releases a significant amount of energy.

103
Q

Which releases more energy for a given mass of fuel, fusion or fission?

A

Fusion

It releases more energy than fission.

104
Q

What conditions are necessary for nuclear fusion to occur?

A

High temperatures and pressures

This is required to overcome the electrostatic repulsion between positively charged nuclei.

105
Q

True or False: Nuclear fusion can occur at low temperatures and pressures.

A

False

High temperatures and pressures are necessary for fusion.

106
Q

Why are current nuclear fusion reactors not economically viable?

A

The temperatures and pressures required are too high

Scientists are still working on developing viable fusion reactors.

107
Q

Why are high temperatures and high pressure needed for nuclear fusion?

A

The particles need to be moving very fast to overcome the strong forces of electrostatic repulsion.

Physics (12 decks)

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