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Radioactivity Flashcards

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1
Q

What is a nuclear symbol

A

The whole square information of the element

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2
Q

What is an isotope

A

Atoms of the same element that have same number of protons but different number of neutrons

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3
Q

Give two properties of isotopes

A

-have different physical properties to each other
-have different stabilities of the nucleus

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4
Q

What causes an isotope to be unstable

A

If there are too few or too many neutrons or protons,
which can disrupt the nuclear force holding the nucleus together

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5
Q

Explain how atoms become stable

A

They emi radiation to become more stable,
Which can be in the form alpha beta or gamma
And this causes energy to be lost from the nucleus, making it more stable

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6
Q

Give two properties of radioactive decay

A

-a random process
-unable to predict when it will happen

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7
Q

What is ionisation

A

The addition or removal of an electron to create an ion

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8
Q

Explain how ionisation occurs

A

The outer electrons absorb energy in the form of ionizing radiation (alpha, beta, gamma), causing them to leave the atom
This means that the atom contains more protons than electrons, so it will become a positively charged proton

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9
Q

What is ionizing radiation

A

-The type of radiation that can ionize atoms that it hits (so cause it to go from atom to ion)
-The examples are alpha beta and gamma

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10
Q

What is an alpha particle

A

A helium nucleus, because it contains two neutrons and two protons

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11
Q

Why is a beta particle and how is it formed

A

A fast moving electron,
which is emitted from a nuclei
when a neutron decays into a proton and electron

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12
Q

What is a gamma ray

A

An electromagnetic wave with the most amount of energy out of all the electromagnetic waves

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13
Q

Charge of alpha particle

A

2+

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14
Q

Charge of beta particle

A

1-

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15
Q

Charge of gamma ray

A

0

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16
Q

RAM of alpha particle

A

4
(2 protons and 2 neutrons)

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17
Q

RAM of beta particle

A

Virtually none or 1/1800

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18
Q

RAM of gamma ray

A

None, because it’s a wave so has no mass

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19
Q

Order the penetrating powers of the 3 types of radiation,
From most penetrating to least penetrating, and explain why

A

Gamma (a wave so can travel quite far)
Beta (moderately penetrating)
Alpha (least penetrating because largest size)

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20
Q

Explain why …. Are the least penetrating but the most ionizing forms of radiation

A

Alpha particles
Least penetrating because of their large mass and size
Most ionizing because of their 2+ charge, so can easily knock electrons off

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21
Q

State how far each form of radiation can travel in air, in order of the most penetrating to least penetrating

A

Gamma rays: infinite distance in air
Beta particles: few 10s cm in air
Alpha particles: few cm in air

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22
Q

Alpha particles are stopped by….

A

Sheet of paper

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23
Q

Beta particles can travel through…. But are stopped by…

A

Sheet of paper
Few mm of aluminum

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24
Q

Gamma rays can travel through… but are partially stopped by

A

Sheet of paper + few mm of aluminum

Few mm of lead

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25
Q

State which material each type of radiation is stopped by

A

Alpha: sheet of paper
Beta; few mm of aluminum
Gamma: few mm of lead (but only partially stopped by it)

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26
Q

When a substance undergoes radioactive decay, state the four types of radiation that can be emitted

A

Alpha
Beta
Gamma
Neutron

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27
Q

State how a neutron can be emitted through radio active decay

A

If the nuclei of the atoms contains too many neutrons, then they will be released to make the atom more stable

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28
Q

State two ways to detect radiation

A

Using a Geiger- Müller tube
Using photographic film

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29
Q

Describe how a Geiger muller tube works

A

It absorbs radiation
which is the transmitted as an electrical impulse
To either a counter which displays the count rate
Or as a clicking sound

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30
Q

What is the count rate, when using a Geiger muller tube

A

The number of decays detected per second

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31
Q

Describe how photographic film can be used to detect radiation

A

It consists of different materials like aluminum and lead and becomes darker when it absorbs some radioactive material

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32
Q

Explain which types of radiation are likely to be detected on a photographic film badge

A

Alpha radiation is unlikely to be detected as it will be absorbed/stopped by the paper
Beta radiation is likely to be absorbed by the aluminum
Gamma radiation is likely to be detected throughout the badge, however some of the radiation may be absorbed by the lead

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33
Q

The radiation received by a person is measured in…., and can lead to..

A

SIEVERTS (sv)
Acute radiation poisoning

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34
Q

Describe the experiment on how you can investigate the penetrating powers of radiation

A

1)Connect the Geiger muller tube to a counter and measure the background radiation, without any sources nearby
2)repeat 3 times and then take an average
3) take out a radioactive source using tongs, and place a fixed distance near to the tube
4)take an absorber, and place it in between the tube and the source, and then take a reading after a one minute interval
5)repeat with different absorbers
6)then repeat the whole experiment again with a different source

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35
Q

Give two safety precautions when investigating the penetrating powers of radioactive sources

A

1)always keep the source a distance away from you
2)use a lead lined container to store the materials at all time

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36
Q

Give three ways that you can ensure minimum errors in the experiment to investigate penetrating powers

A

1)use a material with a long half life and activity
2)when measuring background radiation, make sure sources are a good distance away to avoid disruptions
3)make sure all repeats of the experiment are done in the same location so that they have the same background radiation

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37
Q

What is background radiation

A

The radiation that exists all around us all the time

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38
Q

State 4 types of natural sources that emit background radiation

A

-radon gas from uranium that decays
-cosmic rays from space
-carbon-14 in all organic matter
-in good and drink, eg potassium-40 in bananas

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39
Q

Explain how radon gas is a source of background radiation, and how it’s dangerous

A

Uranium, a naturally radioactive material found in rocks
Can decay into radon gas
Which emits alpha particles
Which if inhaled into lungs can be dangerous

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40
Q

Explain how cosmic waves from space become a source of background radiation

A

The sun emits protons
Which enters the earth at high speeds,
Then these protons collide with molecules in the air which produces gamma rays

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41
Q

State three examples of man made background radiation

A

Medical sources such as X-rays, CT scans and radioactive tracers
Nuclear fallout from nuclear weapons
Nuclear accidents

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42
Q

Give four uses of radioactivity

A

-alpha particles in smoke detectors
-beta particles in thickness gauges
-gamma rays in radio therapy and tracers
-sterilizing food and equipment

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43
Q

Explain how alpha particles are used in smoke detectors

A

1)a radioactive source emits alpha radiation, which ionizes the air around them causing a current to flow in the circuit gap
2)when smoke enters, they absorb the alpha particles (which have a weak penetration power)
3)so the current will stop
4)the alarm can no longer detect a current and this triggers the alarm

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44
Q

Explain how beta particles are used in thickness gauges

A

1)the material passes through between a detector and beta emitter
2) when the material is too thick, more beta particles are absorbed and less penetrate through and are detected
3) and then when the material is thinner, less beta particles are absorbed and more penetrate through and are detected
4)the machine is thus able to make adjustments inorder to keep the thickness at a constant rate

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45
Q

Explain why beta particles are used in thickness gauges and not alpha or gamma

A

Beta particles are partially penetrating,
But if alpha were used which are weak penetrators, they would all be absorbe3d by the material and none would be detected
And if gamma particles used, which are strong penetrators, then almost all would penetrate through and be detected, so the machine would not be able to detect changes in thickness

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46
Q

Explain why alpha particles are used in smoke detectors and not beta or gamma

A

Alpha particles are strongly ionizing and so can create a current
Beta and gamma would not be able to with their ionizing ability

Alpha particles are also weakly penetrating so are able to be absorbed by the smoke and stop the current
Beta which is partially penetrating and gamma which is highly penetrating would simply pass through the smoke and would not be able to stop the current

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47
Q

Explain how radiotherapy works

A

Beams of gamma rays are directed at the cancerous tumor
The gamma rays are highly penetrating so are able to penetrate through the body

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48
Q

Explain how a radioactive tracer works

A

A Radioactive tracer is a radioactive isotope which is injected or swallowed into the body
This emits beta or gamma radiation which penetrates through the body and can be detected externally
So doctors can monitor whether or not particular organs are working properly

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49
Q

Which type of particles are used for radioactive tracers and explain why

A

Beta or gamma particles because they are penetrating and not ionizing swo can not damage cells

Alpha particles are weakly penetrating and strongly ionizing so would be able to kill healthy cell

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50
Q

Give a property that the radioactive isotope in a medical tracer must have and explain why

A

A short half life
So that initially levels can emit large amounts of radiation to be detected
But so that it will quickly disappear from the patient

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51
Q

Give two properties that gamma rays used to sterilize medical equipment must have and why

A

Must have a long half life so that they dont need to be replaced very often
Must be a strong source of gamma so that it is strongly penetrating

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52
Q

Why is sterilizing food better than boiling it to kill microbes

A

Because no high temperatures are used so the food can remain undamaged

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53
Q

Give two definitions of half life

A

The amount of time required for the sample of radioactive nuclei to halve
Or
The amount of time required for the activity(the number of decays) to halve

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54
Q

What is activity

A

The overall rate of decay of all the isotopes in the sample

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55
Q

What is activity measured in

A

Bequerels

56
Q

3 Bequerels is the same as saying

A

3 radioactive nuclei decay per second

(Because remember that Bequerels is activity, which is the rate of decay)

57
Q

Carbon 14 has a half life of 5700 years, explain what this means
Give two interpretations

A

It means that it takes 5700 years for the sample to become 50 percent of its origina value
Or
It takes 5700 years for the activity, or the number of decays per second to become half of what it originally was

58
Q

Explain why activity decreases over time

A

Because as time increases, the number of radioactive (unstable)nuclei in the sample decreases
So there are less nuclei left to decay
So therefore the overall activity decreases

59
Q

Why is contamination more harmful than irradiation

A

Because of the continuous exposure to radiation
Because in irradiation, once the source is removed the object will no longer be exposed to radiation
But once a radioactive isotope goes onto an object, it will keep emitting radiation

60
Q

Explain what it means if a substance has a short half life
And what it means if it has a long half life

A

Short half life means that it has a higher activity,
So has a higher rate of radioactive emissions

Long half life means that it will stay active for longer
So more care is required to control it for longer, with mechanisms such as shielding or storage

61
Q

Definition of contamination

A

The unwanted presence of materials containing radioactive isotopes on other material,
Where this causes the other material to begin to emit radiation and become radioactive itself

62
Q

Definition of irradiation

A

The process of exposing a material to alpha, beta, or gamma radiation,
Where the material itself exposed however will not become radioactive

63
Q

Explain how contamination can occur

A

When a radioactive isotope gets onto another material where it should not be
This causes the material itself to begin to emit radiation and become radioactive itself

64
Q

Why does irradiation not make objects become radioactive

A

Because an object will only become radioactive if it contains radioactive isotopes
But in irradiation the object will only be exposed to the radiation coming from the radioactive isotope itself

65
Q

Give two difference between irradiation and contamination

A

In contamination, the object will contain the radioactive isotope,
But in irradiation, the object will only be exposed to the radiation emitted by the radioactive isotope

In contamination, the object will remain radioactive as long as the source is on it or in it, and even when it is removed, it is difficult to remove the radiation,
But in irradiation, the effect of the radiation emitted by the source will stop as soon as the radiation is removed

66
Q

Explain a method of protection when dealing with contamination,
And describe which type of people deal with contamination

A

-Use an airtight suit because this means that the radioactive atoms can not get inside the person
-people dealing with radiation leaks

67
Q

Explain a method of protection when dealing with irradiation,
And mention which type if people may use this

A

Use a lead lined suit
So that the radiation can be absorbed by the suit, which could otherwise hit the person
Often used when getting an x ray

68
Q

Sources with ….. half-life’s present a greater risk with irradiation because…
And sources with …. Half life present a greater risk with contamination because..

A

Short, because they have a higher activity so a higher rate of radioactive emissions
Long, because they will stay active for longer so need longer care and control, eg storgage

69
Q

Give four methods that can be used to protect oneself against irradiation when dealing with radioactive sources

A

-wear a lead lined suit
-wear gloves and use tongs to keep it a safe distance away
-make sure the source is stored in a lead lined container
-limit the amount of time you are exposed to it to

70
Q

Explain which type of radiation is most dangerous outside the body and which is not and why

A

Beta and gamma radiation are the most dangerous because they are partially and highly penetrating so can penetrate through the skin

Alpha is weakly penetrating
and can be stopped by dead skin cells
and can by stopped by a short distance of air

71
Q

Explain which type of radiation is most dangerous inside the body and why

A

Alpha is most dangerous because it is strongly ionizing so can mutate cells or damage them

Beta and gamma are least dangerous because they are weakly ionizing

72
Q

Explain why ionizing radiation is dangerous to humans, discussing the two main possible things that can happen

A

Dangerous because can either damage dna, killing the cells
Or can mutate the dna, which if replicated, can form a tumor, leading to cancer

73
Q

Give two other possible things that can happen if a person has acute radiation exposure

A

Can cause skin burns
Can reduce amonts of white blood cells making you more prone to infection

74
Q

Give four precautions when dealing with radiation

A

-wear protective clothing such as lead lined suits or airtight suits
-when not in use, store radioactive sources in lead lined containers
-keep a safe distance from the source by using gloves and tongs
-limit the amount of time of exposure to the radioactive source,

75
Q

How can you monitor the amount of dosage of radiation that you receive, and what does this measure the dosage of radiation received in

A

Use a dosemeter
Which measures dosage of radiation in Sieverts

76
Q

Explain why and how substances with a long half life should be treated

A

Sources with a long half life remain active for longer and so decay at a slower rate
This means that they are often buried underground to prevent radioactive emissions from being released into the environment

77
Q

Definition of nuclear fission

A

The splitting up of large and unstable nuclei into smaller nuclei, releasing large amounts of energy

78
Q

What are the two ways that nuclear fission can occur, and describe them

A

Spontaneous fission:
-when no additional energy is required for the fission to occur
-but is rare

Absorbing a neutron:
-when a neutron must be added so that it can be absorbed by the large and unstable nuclei
-so that it becomes more unstable and decays immediately

79
Q

What are the two characteristics that a nuclei must have inorder for it to undergo nuclear fission

A

Must be large
Must be unstable

80
Q

State two characteristics that the daughter nuclei have

A

They are lighter than the original nuclei
They are also radioactive

81
Q

Why are …. Moving neutrons used in nuclear fission to make the nuclei unstable and decay

A

Slow
Because they are more easily absorbed by the nuclei

82
Q

Explain how nuclear fission occurs

A

1)a slow moving neutron is fired at a large and unstable nuclei such as Uranium-235
2)This uranium nuclei absorbs this neutron, but the addition of the new neutron makes the nuclei more unstable
3)this causes it to split into two daughter nuclei and along with this, two or three neutrons are also released
4)these neutrons then go onto hit another uranium-235 nuclei, causing it to split apart and the process continues, this is called a chain reaction
5) with every fission reaction, gamma rays are released,
Aswell as large amounts of energy, which is then later transferred from nuclear potential energy to kinetic energy where using a nuclear power station, is converted into electrical energy

83
Q

State the energy stores involved in the energy emitted from nuclear fission inorder to generate electricty

A

Energy is transferred from nuclear potential energy to kinetic energy
And then using a nuclear power station is transferred into electrical energy

84
Q

What is a chain reaction

A

Process in nuclear fission, where neutrons released go onto hit another large and unstable nuclei causing it to split into more smaller nuclei and more neutrons, where this fission process continues onto another nuclei. The process repeats and this is the chain reaction

85
Q

What is the function of a nuclear reactor

A

To control the chain reaction
So that the energy released from nuclear fission can safely be harnessed
And then used to make electrical energy in a nuclear power plant

86
Q

Function of the control rods

A

To absorb neutrons to limit the rate of fission occurring

87
Q

Explain how the control rods work

A

They are adjusted lower or higher so that for every 2 or 3 neutrons released from a fission reaction, only one neutron goes on to produce further fission reactions

88
Q

How can you shut the nuclear reactor completely down

A

Lower the control rods all the way so that all the neutrons are absorbed and no more fission can take place

89
Q

What happens if you lower the control rods deep

A

More neutrons are absorbed so the rate of fission decreases

90
Q

What happens if you only lower the control rods a small amount

A

Then only a small amount of neutrons will be absorbed so the rate of fission increases

91
Q

What are the control rods made of

A

Boron because able to absorb neutrons easily

92
Q

What is the function of the fuel rods

A

They are where the fission reactions take place

93
Q

What is the function of the moderator

A

To slow the neutrons down so that they can be more easily absorbed by U-235 in the fuel rods

94
Q

Explain how the moderator works

A

Fast moving neutrons produced by fission, collide with the molecules in the moderator, which slows them down as they lose momentum
They reach thermal equilibrium with the moderator and so the neutrons are now called thermal neutrons
They can now be more easily absorbed by the U-235 in the fuel rods

95
Q

What is the moderator made of

A

Graphite

96
Q

What is the purpose of shielding in a nuclear reactor, and what two materials is it made of

A

To absorb the harmful ionizing radiation
Made of steel and concrete

97
Q

What is the function of the coolant

A

It absorbs and transmits the heat energy produced in fission
Which is then used to turn water into steam
Where this steam is used to turn a turbine
Which is used to turn a generator
Which generates electricity

98
Q

Give three advantages of using nuclear energy

A

-reliable because not dépendant upon the weather
-it is clean, so does not produce any green house gases
-less nuclear fuel would be required for the amount of fossil fuels required for the same amount of energy

99
Q

Give three disadvantages of using nuclear energy

A

-expensive to decommission
-difficult and expensive to dispose of the radioactive waste released as it must be buried underground
-risk of major disaster such as radiation leak

100
Q

Why is fusion really difficult to achieve

A

Inroder for the two nuclei to fuse, they must get close together
Which is difficult because they repel each other due to similar charges
So to overcome this they need to be travelling at really high speeds, so have to have high kinetic energy
To do this This requires really high temperatures and pressures

101
Q

What is nuclear fusion

A

The process where two light nuclei join together to form a heavier nucleus

102
Q

Why does nuclear fusion only occur in stars

A

Because it requires extremely large amounts of temperature and pressure

103
Q

Explain why nuclear fusion creates such large amounts of energy

A

Because some of the mass of the original two nuclei are converted into energy, rather than being transferred to the helium nucleus

104
Q

The energy produced from a fusion reaction can be calculated using what equation?
And state what each variable means

A

E=MC^2

E=total amount of energy released from fusion
M= mass converted into energy
C=speed of light

105
Q

State and describe the three conditions required for fusion to occur

A

Must have very high temperatures
Must have very high densities/ pressures inorder to increase the possibility of collisions
Nuclei must be traveling at very high speeds with large amounts of kinetic energy inorder to overcome forces of repulsion

106
Q

Name two common fuels used in nuclear fission

A

Uranium or plutonium isotopes

107
Q

If fusion were possible, give three advantages it would have over fission

A

1)would produce more energy
2)fuel would be more plentiful than uranium and plutonium
3)would be safer because less radioactive waste produced

108
Q

Describe the structure of the atom

A

It has a positively charged nucleus made up protons and neutrons.
And then it has electrons that orbit the nucleus

109
Q

Give the relative masses of the subatomic particles of an element

A

Proton: 1
Neutron:1
Electron 1/1835

110
Q

What types of radiation are ionizing

A

Alpha
Beta
Gamma
(Not neutron radiation)

111
Q

In which process does a neutron turn into a proton and emit a fast moving electron

A

Beta decay

112
Q

What effect does beta decay have on the mass number and at atomic number of an element

A

Atomic number increases, because during beta decay, a neutron changes into a proton, so it thus has one more proton
The mass number stays the same because the overall number of protons and neutrons is the same(as it has gained a proton but lost a neutron)

113
Q

When are gamma rays released form an atom

A

When an atom decays and releases alpha or beta, there is still some excess energy that needs to be released
So is released in the form of gamma
And gamma always happens alongside alpha and beta, never alone

114
Q

Is long half life more dangerous or short half life

A

Long half life because this means that it will remain radioactively active for longer
So more dangerous

115
Q

What precautions are taken to reduce harm to both patients and doctors when using radioactive decay

A

Both wear protective clothing such as lead suits
Given radiation with a short half life, so that although the initial levels will be high enough to detect, it has a short activity so will dissapear from the patients body

116
Q

Give a way that you can treat tumours internally, and then externally, and mention the type of radiation used

A

Internally, using medical tracers, which often use beta or gamma radiation

117
Q

How is electricity generated in a nuclear power station

A

Nuclear fission reactions release nuclear energy
This is converted to thermal energy
This thermal heat energy is then used to turn water into steam
Steam is used to turn a turbine
Turbine is used to turn a generator
Generator e generates electricity in a nuclear power station

118
Q

What is the type of energy released in a fission reaction

A

Kinetic energy

119
Q

In terms of neutrons, how is nuclear fission controlled

A

Control rods absorb neutrons
To limit the rate of fission
So that for every two or three neutrons, only one neutron goes on to cause a fission reaction

120
Q

When doing an experiment to investigate radiation, materials of various thickness will be used.
How do you know which material is the best absorber of radiation, by looking at the count rate of the sources used with it

A

The material which has the lowest count rate
Because this means that the least amount of radiation was able to penetrate through and be detected by the detector
Meaning it was absorbed by the material

121
Q

Give two reasons why you should use substances with a …. Half life when investigating radiation

A

Long
Because a longer half life means less activity, so they will be less hazardous
Because the count rate is more likely to be constant and so will not need to be constantly replaced (bc remeber that radioactive decay is a random process, so if it takes longer to decay, that means that probability that it will completely decay is less)

122
Q

Granite is a rock.
It contains a radioactive isotope of uranium that decays very slowly.
(i) Explain how scientists can use this radioactivity to find the age of a piece of granite.

A

thereisaknownproportion/composition/ activity when rocks formed; any FOUR from:
MP2. measure/determine the proportion of
uranium or the activity now;
MP3. compareactivitynowtooriginalactivity/eq;
MP4. (hence)determinethetime/numberof half-lives elapsed;
MP5. (hence)calculateagefromreferenceto half-life;

123
Q

Why is shielding required (3)

A

Because the waste released from the nuclear reactor is radioactive
So it absorbs hazardous ionizing radiation
Which can damage cells and mutate dna, causing cancer

124
Q

Definition of unstable

A

The ability to decay and emit radioactive particles such as alpha or beta, or they emit gamma

125
Q

There are two sources of alpha radiation in some houses:
radon gas in the air
solid americium in a smoke alarm
The alpha particles from radon are a greater risk to health than the alpha particles
from americium.
Explain why, giving two reasons

A

Because radon gas is a gas and is mobile
Americium is a solid so stays in the smoke alarm

Radon can escape and be inhaled and damage internal tissue
Americium are absorbed by the smoke detector

126
Q

Which out of the three electromagnetic radiations has the highest speed

A

Gamma rays

127
Q

What effect does the emission of a beta particle have on a nucleus

A

Neutron changes Into a proton
Therefore neutron number decreases by 1

Neutron changes into a proton
Therefore proton number increases by

128
Q

Describe a method to find the corrected count rate (4 marks)

A

-move source far away from detector
-measure background radiation for a specific amount of time by observing count rate
-repeat three times and take an average
-minus new count rate from old count rate to find corrected count rate

129
Q

Why is it important that the control rods are not lifted too high

A

Because then less neutrons will be absorbed
So the rate of the fission reaction will be too high
So it will emit amounts of energy that are extremely large
Which could lead to a meltdown of the reactor

130
Q

A scientist wants alpha particles to hit a screen, so he removes the air from the container he does this in.
Explain why he does this

A

Because alpha particles have a short range(short penetrating power) in air
So would not be able to reach the screen

131
Q

What are the three things Rutherford found from his gold leaf experiment

A

-some alpha particles went straight through, meaning an atom is mostly empty space
-some were deflected a small amount, meaning the atom constats of protons, positively charged
-some bounced right back

132
Q

Explain why alpha particles are less penetrating than beta (4)

A

Have larger mass, bc helium nucleus, so ram of 4,
But beta has mass of 1/1800

So alpha can collide more readily with other atoms, making it difficult to penetrate through

Alpha particles also have a higher charge and are more ionizing

133
Q

Explain why if a radioactive isotope with a long half life is absorbed by the body, that this is dangerous

A

Because long half life means that it stays active for longer
So decays at a slower rate
Therefore all of the radiation emitted by it will be absorbed by the bones and can
Be hazardous, eg damaging cells or mutating dna creating a tumour, causing cancer

134
Q

Explain why strontium-90 and yttrium-90 can both be described as isotopes, even though they have different numbers of protons.

A

Because they are isotopes of different elements
Therefore strontium will have same number of protons as other strontium atoms
And yttrium will have some number of protons as otehr ytrriuk atoms

135
Q

Explain why beta radiation is good for treating cancer with internal methods

A

Less penetrating than for example gamma, so can not travel outside the body
And is absorbed by the tumor
And reduces risks to Damaging and killing other healthy cells

136
Q

Give the nucleon number, and the proton number of a neutron

A

Nucleon= 1
Mass=0

physics (10 decks)

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