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A-Level PHYSICS Edexcel > Topic 11 - Nuclear Radiation > Flashcards

Topic 11 - Nuclear Radiation Flashcards

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1
Q

What does an atom do if its unstable

A

it breaks down to become more stable

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2
Q

What is instability caused by?

A
  • too many neutrons
  • no enough neutrons
  • too much energy in the nucleus
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3
Q

Structure of Alpha

A

helium nucleus (2 protons, 2 neutrons)

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4
Q

Structure of Beta

A

Made of single electron (no mass)

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5
Q

Structure of Gamma

A

short wavelength, high frequency electromagnetic wave

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6
Q

Range of alpha in air

A

between 2cm-10cm (loses energy due to interactions)

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7
Q

Range of Beta in air

A

a few metres (17m)

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8
Q

Range of Gamma in air

A

Very long/ infinite (no charge/mass)

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9
Q

Penetration of alpha

A

weak (absorbed by paper)

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10
Q

Penetration of Beta

A

absorbed by 3mm of aluminium

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11
Q

Penetration of Gamma

A

absorbed by metres of lead

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12
Q

Ionising ability of alpha

A

strong

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13
Q

Ionising ability of beta

A

weakly

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14
Q

Ionising ability of gamma

A

very weakly

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15
Q

speed of alpha

A

slow

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16
Q

speed of beta

A

fast

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17
Q

speed of gamma

A

speed of light

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18
Q

is alpha affected by B-fields

A

yes

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19
Q

is beta affected by B-fields

A

yes

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20
Q

is gamma affected by B-fields

A

no

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21
Q

uses of alpha

A

smoke detectors, cancer treatment, poisin

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22
Q

uses of beta

A

tracers, monitoring material thickness

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23
Q

uses of gamma

A

cancer treatment, sterilising equipment

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24
Q

what emits background radiation?

A

rocks, cosmic radiation, living things, manmade radiation, air

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25
Q

How to account for background radiation

A

record it before you do the experiment and subtract it from the totals

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26
Q

method of detecting radiation

A
  1. photographic film
  2. leaf electroscope
  3. cloud/bubble chambers
  4. Geiger Muller tube
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27
Q

Geiger Muller Tube

A

when any type of radiation enters the tube it produces ions in the gas, enabling the tube to conduct and complete the circuit. This creates a voltage pulse which is outputted, amplified and counted.

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28
Q

Photographic Film

A

where the film has been exposed to radiation it darkens

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29
Q

Leaf electroscope

A

a radioactive source ionises the air discharging the electroscope

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30
Q

Cloud/Bubble Chambers

A

a radioactive source ionises and condenses the alcohol leaving a trail

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31
Q

Ionisation

A

radiation is very energetic and knocks electrons off molecules

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32
Q

Why is alpha the most ionising

A

its heavy and slow moving with the strongest charge meaning it interacts strongly with matter

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33
Q

Dangers of ionising radiation

A
  • release lots of energy and cause burning
  • changes the chemistry of cells causing radiation sickness or hair loss
  • cells may be genetically changed causing cancer
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34
Q

Inverse square law for gamma radiation

A
  • gamma rays always spread out away from the source.

- the intensity of gamma follows an invers square

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35
Q

When does an inverse square apply for alpha and beta

A

in a vacuum so that no interaction can occur

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36
Q

how is a nucleus held together

A

strong nuclear force

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37
Q

why would a nucleus not hold together without the strong nuclear force?

A

its made up of many positive charges which would all repel by the electrostatic force of repulsion

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38
Q

stable nuclei

A

electrostatic and strong nuclear forces are balanced

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39
Q

unstable nuclei

A

electrostatic forces and strong nuclear forces are not balanced. they try to become more stable by emitting alpha, beta or gamma

40
Q

daughter nucleus

A

when a parent nucleus attempts to become more stable it emits alpha or beta particle its left with a different number of protons and neutrons

41
Q

parent nucleus

A

the original unstable nucleus

42
Q

alpha decay

A

produced when a large unstable nucleus decays

43
Q

Beta decay

A

produced when a neutron changes to a proton also produces a neutrino

44
Q

How do we a neutrino is produced in beta decay?

A

The beta particles are emitted with a range of energies that can only be explained if another particle was emitted

45
Q

neutrino with beta - decay

A

electron antineutrino

46
Q

neutrino produced with beta + decay

A

electron neutrino

47
Q

When does beta + decay happen

A

for nuclides below the stability line

48
Q

When does beta - decay happen

A

for nuclides above the stability line

49
Q

Gamma decay

A

the release of energy from a nucleus which leaves the structure of the nucleus otherwise unchanged

50
Q

When does gamma often occur

A

after alpha/beta emission because the nuclei is left in an excited state

51
Q

Electron capture

A

when an unstable nucleus captures an orbital electron from one of its lowest energy levels. A proton then changes to a neutron and a neutrino is emitted.

52
Q

When doe electron capture happen?

A

for nuclides below the stability line

53
Q

Why can you no predict nuclear decay

A

it spontaneous and random

54
Q

How can you try and measure decay

A

calculate the probability of decay. Every type of isotope decays a different rate but particular isotopes decay at the same rate.

55
Q

decay constant, λ

A

the probability that an individual nucleus will decay within a unit of time

56
Q

activity, A

A

the number of nuclei that decay in a unit of time

57
Q

activity/ decay constant equation

A

A = λN

58
Q

half life, Τ

A

the average time is takes for the number of undecayed nuclei to half

59
Q

decay constant and half life equation

A

λ = ln2/Τ

60
Q

finding the half life from an exponential decay graph

A

read the time when N is half the original value

61
Q

how do carbon dating work

A

all living things take in carbon-14 and when they die this stops. Over time carbon-14 decays and so the amount of carbon-14 in an ancient specimen can be used to date bones

62
Q

How to age rocks

A

measure how much uranium-235 has changed to lead-206

63
Q

mass defect

A

the difference in mass

64
Q

Einsteins equation

A

E = mc^2

65
Q

How is extra mass explained

A

the total amount of mass and energy is conserved E = mc^2

66
Q

binding energy

A

The energy needed to separate a nucleus into individual protons and neutrons

67
Q

What makes a nucleus more stable

A

if it has a higher binding energy per nulceon

68
Q

What does the daughter nucleus always have

A

a higher binding energy per nucleon than its parent

69
Q

1 atomic mass unit, u

A

1.66x10-27kg

70
Q

Nuclear Fission

A

A slow moving neutron is fired at a heavy nucleus which absorbs it and making it unstable. This causes it to split into daughter nuclei and excess neutrons.

71
Q

How does nuclear fission work

A

the strong nuclear force only acts over a short distance so when a neutron is absorbed it displaces particles possibly allowing the electrostatic force to overcome strong nuclear force

72
Q

chain reaction

A

when the neutrons released from one reaction go on to cause another reaction

73
Q

Nuclear fusion

A

when smaller nuclei combine to produce larger nuclei and release energy in the process.

74
Q

Why is Fusion better than Fission

A
  • power output per kilogram is greater
  • raw materials are cheap and easily available
  • no radioactive waste is produced (if there is some it has a very short halflife)
75
Q

How does fusion occur in stars?

A
  • proton fuses with proton, forming He-2
  • one proton decays to a neutron, leaving H-2
  • another proton fuses with H-2, forming He-3
  • two He-3 nuclei fuse resulting in He-4 and a left over proton which are returned to the process
76
Q

Where does fission occur on the binding energy curve

A

To the right of iron

77
Q

Where does fusion occur on the binding energy curve

A

to the left of iron

78
Q

Advantages of fusion over fission

A
  • power output per kilogram is greater
  • raw materials are cheap and easily available (water)
  • no radioactive waste (if there is any it has avery short half life)
79
Q

What are control rods made of in nuclear power stations?

A

boron (very stable)

80
Q

Random process of decay

A

don’t know when or or which nucleus will decay next. In a given time interval each nucleus has a fixed probability of decay.

81
Q

In smoke detectors when does a stream of alpha particles cause a charge to flow.

A

The alpha particles ionise the air and the ions/electrons move in the uniform electric field between the plates.

82
Q

Spontaneous decay

A

can’t be influenced by external factors

83
Q

Kinetic energy in nuclear fusion method

A
  1. KEa + KEb = Q
  2. conservation of momentum MaVa = MbVb
  3. rearrange Va = MbVb/Ma
  4. find value of Mb/Ma (using relative masses)
  5. find Ea/Eb
  6. Use this proportion and Q to calculate KEa
84
Q

The total number of free neutrons immediately after a fission reaction…

A

increases

85
Q

The mass of the fission fragments is…

A

less than the mass of the nucleus before fission

86
Q

What is required for fission to occur

A

Must absorb neutrons

87
Q

What is true for both fusion and fission

A

Binding energy per nucleon increases

88
Q

radioactive atom

A

has an unstable nucleus with emits alpha, beta or gamma radiation

89
Q

fusion conditions (natural)

A
  • extremely high temperatures to overcome electrostatic repulsion
  • high density for sufficient collision rate
90
Q

fusion conditions (reactor)

A
  • extremely high temperatures to overcome electrostatic repulsion
  • Strong magnetic fields to keep plasma from reactor wall
  • high density/ enough fuel
91
Q

why does fusion release energy

A
  • binding energy per nucleon increases as the number of nucleons increases
  • if binding energy per nucleon increases energy is released
92
Q

why does fission release energy

A
  • binding energy per nucleon increases as the number of nucleons decreases
  • if binding energy per nucleon increases energy is released
93
Q

why does fission require high temperature?

A

high temperature to provide enough energy to overcome the electrostatic repulsive force between
nuclei

94
Q

why does fusion require high density?

A

high density to give big enough collision rate to maintain reaction

95
Q

binding energy

A

The energy equivalent to the mass deficit when nucleons bind together to form an atomic nucleus

96
Q

Alternative unit for activity/ what this means

A

s^-1. You can use it as a time, e.g. P = E/t you could use activity as time

A-Level PHYSICS Edexcel (16 decks)

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