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Physics > Radioactivity & Particles > Flashcards

Radioactivity & Particles Flashcards

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1
Q

Components of an atom

A

Protons, neutrons, electrons, electron shells

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2
Q

Location, relative mass and relative charge of protons, neutrons and electrons

A
  • protons = 1mu, +1, nucleus
  • neutrons = 1mu, 0, nucleus
  • electrons = 1/1836mu, electron shells
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3
Q

How does an atom become an ion

A

Electron loss or gain

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4
Q

Which number is unique to each element?

A

Proton/atomic number

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5
Q

Define atomic number

A

Number of protons in atom

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6
Q

Define mass number

A

Total number of protons and neutrons

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7
Q

Define isotope

A

An atom with the same number of protons but different number of neutrons

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8
Q

What never changes in an isotope?

A

Atomic number

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9
Q

Why do nuclei decay?

A

To become more stable, due to a variety of reasons :
- too many neutrons
- too big (too many protons + neutrons)
- too much energy

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10
Q

What type of process is decay and why?

A

Decay is a random process ; we cannot predict which unstable nucleus in a radioactive isotope will decay or when that decay will occur

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11
Q

What happens to unstable nuclei when they decay and why?

A

They give off radiation in the form of alpha, beta or gamma in order to release energy

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12
Q

What makes radiation ionising?

A

They have enough energy to ionise atoms by stripping electrons off them when they interact

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13
Q

Properties of alpha

A
  • 2 protons + 2 neutrons
  • charge = +2
  • relative mass = 4
  • ionising power = high bc they lose energy quickly + interact w/ atoms a lot due to size and energy
  • penetrating power = low
  • stopped/absorbed by = paper or card
  • range in air = 2-3cm
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14
Q

Properties of beta

A
  • high energy electron
  • charge = -1
  • relative mass = 1/1836mu
  • ionising power =moderate
  • penetration = moderate
  • stopped/absorbed by = thin aluminium foil
  • range in air = around 1m
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15
Q

Properties of gamma

A
  • electromagnetic wave
  • relative mass = almost 0
  • charge = 0
  • ionising power = low
  • penetration = high
  • stopped/absorbed by = thick lead + concrete but it’s hard to stop
  • range in air = 1km+
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16
Q

Alpha damaging and penetration

A

As it’s a big heavy particle, it loses a lot of its energy very quickly. This means that, whilst it does cause lots of damage, it cannot penetrate very far

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17
Q

Beta damage and penetration

A

As it’s small, it has a greater penetration than alpha but won’t cause as much damage

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18
Q

Gamma damage and penetration

A

Electromagnetic wave means that it’s not very ionising but has lots of penetration and can travel for miles before being fully absorbed

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19
Q

Describe the investigation about penetration of different radiation

A
  • measure the cps of each source beforehand over 5 minutes to compare against
  • place alpha source with paper, beta with thin foil, gamma with thick lead
  • they will all drop to background radiation as the materials all absorb those radiations
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20
Q

What does the GM tube do?

A

Geiger-muller tube detects radiation

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21
Q

What does the radioactive source do?

A

Emit radiation

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22
Q

What does the counter do?

A

Records the quantity of radiation penetrating through the materials

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23
Q

Define background radiation

A

Radiation that is ever present and cannot be removed

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24
Q

What is the purpose of measuring over a long period of time?

A

As decay is random, a longer count period improve accuracy by reducing random error

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25
Q

Activity level is measured in…

A

Counts per second (cps)

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26
Q

Range in air of alpha

A

A couple of centimetres

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27
Q

Range in air of beta

A

25cm-1m

28
Q

Range in air of gamma

A

Km+

29
Q

What happens to the nucleus in an alpha decay

A

2 protons + 2 neutrons are ejected from nucleus so atomic number decreases by 2 and mass number decreases by 4

30
Q

What happens to the nucleus in a beta decay?

A

A high energy electron is ejected from the nucleus and a neutron has tuned into a proton , meaning that the atomic number increase by 1 and mass number stays the same

31
Q

What happens to the nucleus when gamma passes through it?

A

Nothing

32
Q

What happens to the nucleus during a neutron decay?

A

Neutron(s) leave the nucleus meaning that the proton number is unchanged and the mass number decreases by however many neutrons are emitted

33
Q

How is ionising radiation detected in a lab?

A

By a GM tube detects radiation

34
Q

What does the radiation badge do? How do they work?

A
  • monitor exposure and warn if there are unsafe levels of radiation
  • photographic film changes colour when exposed to different types of radiation
35
Q

What percentage of background radiation sources are artificial and natural?

A

80% are natural and 20% are artificial

36
Q

What are the sources of artificial background radiation?

A
  • 17.5% medical
  • 0.5% nuclear power + weapons testing
  • 2% other
37
Q

What are the sources of natural background radiation?

A
  • 40% radon gas from the ground
  • 15% buildings + ground
  • 10% cosmic rays
  • 15% humans + food + drink
38
Q

What happens to number of undecayed nuclei of a radioactive source over time?

A

Decreases

39
Q

What happens to decay rate over time?

A

Decreases

40
Q

Definition of half life in terms of undecayed nuclei

A

The average amount of time taken for the number of undecayed nuclei in a radioactive sample to halve

41
Q

Definition of half life in terms of activity levels

A

The average time taken for the activity levels in counts per second to fall to half its original value

42
Q

Irradiation

A

When something is exposed to the ionising radiation from a radioactive source. When the source is removed, the irradiation stops

43
Q

Contamination

A

When the radioactive source gets into/ onto something so it’s being exposed continually

44
Q

How do alpha emitter smoke detectors work?

A
  • alpha emitter ionises air between charged plates that allow current to flow
  • when detector senses current, the alarm doesn’t sound
  • smoke enters the case and absorbs alpha = no ionsisation of air
  • detector senses drop in current so the signal is sent for alarm to sound
45
Q

Why is alpha suitable for smoke detectors? Why is a long HL required? Why can’t you dismantle an alpha emitter smoke detector?

A
  • very ionising = effective ionisation of air + low penetrating power = can’t pass through the hard plastic case
  • long HL = steady activity level + so doesn’t need replacement often
  • dismantle = potential contamination by inhaling or ingesting accidentally
46
Q

How is beta used in a foil factory?

A

If too much beta is detected, then the foil is too thin. If too little is detected, then it’s too thick

47
Q

Why is beta good for foil factory usage? Why does it need a long HL?

A
  • alpha wouldn’t penetrate foil and gamma would either way and beta does but less as thickness increases
  • long HL = less replacement + more regular activity levels
48
Q

How does gamma help in leaky pipe detection?

A
  • gamma emitter is dissolved into water
  • gamma radiation is detected on surface bc of high penetration
  • higher levels of radiation = cracked pip as water is closer to surface
49
Q

Why is gamma good for leaky pipe detection? Why does it need a short HL?

A
  • weakly ionising = less danger posed + high penetration = more likely to pass through the ground
  • short HL = quickly decays to a safe level by the time it reaches people’s homes
50
Q

How is gamma used in sterilisation of surgical equipment?

A
  • surgical equipment or food is sealed and remains sealed meaning that it is only irradiated
  • gamma can kill unwanted bacteria and microorganisms
51
Q

Why is gamma suitable for sterilisation of food and surgical equipment? Why is it safe to use these after?

A
  • gamma can penetrate through package and kills bacteria
  • Food and equipment has been irradiated not contaminated so it is not emitting radiation
52
Q

How is gamma used in radiotherapy?

A

Gamma emitter is directed at cancerous cells repeatedly from multiple angles to ensure that healthy cells are not exposed

53
Q

Why is gamma suitable for radiotherapy?

A
  • it can penetrate through tissues to reach cancerous cells but is still not ionising so will not cause cell damage
  • alpha would not penetrate and beta would be too ionising
54
Q

What are the dangers of ionising radiation?

A

DNA is ionised which damages it and causes mutations and risks cancer. It can also kill cells

55
Q

What are the three ways to limit exposure to ionising radiation?

A
  • Increasing distance from radioactive source
  • limiting exposure time and use of radioactivity detecting badges
  • Shielding through the use of lead aprons for example
56
Q

How does ionising radiation ionise a material?

A

Ionising radiation collides of atoms which become ionised because their electrons are stripped off causing the radiation to lose some of its energy

57
Q

Why does alpha radiation have the strongest interaction with atoms in comparison to beta or gamma?

A

Alpha has the strongest interactions as it has the greatest charge of +2 in comparison to beta with minus one charge and gamma with no charge or or mass

58
Q

Why is Alpha the most ionising?

A

Loses its energy at a faster rate as they lose more energy per interaction with other atoms in comparison to beta or Gamma

59
Q

How are nuclear reactions used as a source of energy?

A
  • thermal energy is released from nuclear reactions which can be used in power stations
  • heat boils water into steam and the steam turns the turbine which turns the generator and generates electricity
60
Q

Describe the process of nuclear fission

A

Parent nuclei absorbs a neutron, this causes it to become unstable. Parent nuclei then splits into smaller daughter nuclei and spare neutrons are also emitted as well as gamma radiation and excess energy

61
Q

How how does one fission event cause a chain reaction?

A

Multiple spare neutrons from each fission event can go onto collide with other large nuclei causing an exponential growth in the number of events unless controlled

62
Q

Nuclear fuel rod function

A

Rod containing radioactive material and allows spare neutrons to travel to neighbouring rods to continue fission events

63
Q

Movable control rod function

A

Lowered into core to control the rate of chain reaction by absorbing excess neutrons

64
Q

Graphite core/moderator

A

Absorb some energy of neutrons so that they are more likely to cause fission in next rod

65
Q

Coolant function

A

Transfer thermal energy to nearby boiler to drive turbines and generators

Physics (10 decks)

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