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Physics: paper 1 > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What is an atom

A

A positively charged nucleus surrounded by negatively charged electrons

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2
Q

What is the size of atom

A

0.1 nanometres (10^-10)

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3
Q

What is the relative mass and charge of a proton

A

Relative Mass: 1
Relative Charge: +1

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4
Q

What is the relative mass and charge of a neutron

A

Relative Mass: 1
Relative Charge: 0

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5
Q

What is the relative mass and charge of a electron

A

Relative Mass: 0.0005
Relative Charge: -1

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6
Q

What is the relative mass and charge of a positron

A

Relative Mass: 0.0005
Relative Charge: +1

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7
Q

What is an isotope

A

An element with same amount of protons but different amount of neutrons

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8
Q

What is the mass number of an atom

A

no* neutrons + protons

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9
Q

What happens when an electron moves to a high orbit (away from the nucleus)

A

The atom has absorbed EM radiation

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10
Q

How does an electron become an ion

A

When it gains enough energy to leave the atom

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11
Q

What does it mean for an electron to be excited

A

It has absorbed EM radiation

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12
Q

What happens to an excited electron in an atom

A

It moves to a high orbit (moving away from the nucleus and onto a further shell)

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13
Q

What happens when an electron loses energy

A

electron falls to a low orbit (closer to the nucleus)

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14
Q

What are the 4 main forms of decay

A
  1. Alpha
  2. Beta
  3. Gamma
  4. Neutron
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15
Q

How is radioactive decay emitted

A

By an unstable nuclei

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16
Q

Why are most isotopes unstable

A

1- Big in size
2- Excess/ limited amount of neutrons

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17
Q

Describe the properties of an alpha particle (α)
(3 points)

A
  1. Same as a helium nucleus
  2. 2 protons, 2 neutrons
  3. 2+ charge
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18
Q

Describe the ionising and penetrating levels of an alpha particle

A
  1. Highly ionising
  2. Weakly penetrating
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19
Q

What is a beta minus β- particle

A

Fast-moving electrons emitted from the nucleus

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20
Q

What is a Beta plus particle

A

Fast moving positrons produced when a neutron changes into an electron and proton

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21
Q

Describe the ionising and penetrating levels of a Beta particle

A
  1. Moderately ionising
  2. Moderately penetrating
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22
Q

Charge of a beta minus particle and beta plus particle

A

Beta minus = -1
Beta plus = +1

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23
Q

Describe the properties of gamma rays γ

A
  1. Electromagnetic waves
  2. No charge or mass
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24
Q

Describe the ionising and penetrating levels of Gamma rays

A
  1. Low ionising
  2. Highly penetrating
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25
Q

What material is able to stop Alpha radiation

A

Paper or the outer layers of skin

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26
Q

What material can absorb Beta radiation

A

a few mm of Aluminium

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27
Q

What material can absorb gamma rays

A
  1. metres of concrete
  2. several centimetres of lead
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28
Q

What is background radiation

A

radiation that exists around us all the time

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29
Q

What are 3 natural sources of background radiation

A
  1. Radon gas from rocks and soil
  2. Cosmic rays from space
  3. Radioactive material in foods (i.e bananas)
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30
Q

What are 3 man-made sources of background radiation

A
  1. Medical sources
  2. Nuclear fallout after a nuclear explosion
  3. Nuclear accidents such as Chernobyl
31
Q

How can photographic film be used to measure background radiation

A

Film is initially white and turns black as more radiation is absorbed

32
Q

How does a Geiger-Muller tube measure radiation

A
  1. As it absorbs radiation, it transmits an electrical pulse to the tube
  2. Tube produces a clicking sound.
  3. Higher the frequency of clicks, the more radiation present.
33
Q

Describe the process of β– decay

A
  1. emitted by nuclei with too many neutrons
  2. neutron changes into a proton and an electron
  3. electron is emitted & proton remains in nucleus
34
Q

How does beta minus decay affect the element

A

Atomic number increases by +1

35
Q

Describe the process of β+ decay

A
  1. Emitted by nuclei with excessive protons
  2. Proton turns into a neutron emitting a positron
  3. Positron = emitted
    Neutron = remains in nucleus
36
Q

How does Beta+ decay affect a nuclei

A

Atomic number decreases by -1

37
Q

What is the nuclear transformation for alpha emission

A
  1. The atomic (proton) number decreases by 2
  2. The mass (nucleon) number decreases by 4
38
Q

What is the nuclear transformation for gamma radiation

A

No protons or neutrons are lost and therefore nothing changes

39
Q

Describe neutron emission

A
  1. The atomic (proton) number does not change
  2. The mass (nucleon) number decreases by 1
40
Q

What usually happens after the radioactive decay of a nuclei

A

often have excess energy which is released as gamma when atom rearranges

41
Q

Define activity within radiation decay

A

The rate at which the unstable nuclei from a source of radiation decays

42
Q

What is the unit for activity and what does it equate to

A

Becquerels (Bq) = 1 nucleus in the source decaying in 1 second

43
Q

What is half-life

A

The time taken for half the undecayed nuclei to decay or the activity of a source to decay by half

44
Q

Can half-life be predicted?

A

No; however the rate that the activity decreases can be predicted

45
Q

How do you work out net decline

A

initial number - number after X half-lives / initial number

46
Q

How do you measure the half-life of a sample

A
  1. Measure the initial activity, A0, of the sample
  2. Determine the half-life of this original activity
  3. Measure how the activity changes with time
47
Q

How is radiation used in radiotherapy

A

Gamma rays are used onto the tumour killing it’s DNA therefore slowing/killing cancerous cells

48
Q

How is radiation used in tracers

A

Gamma/Beta is injected into the body and using an external detector it’s progress is followed around the body - tests to see if organs are absorbing the right amount and if not flags up cause for concern

49
Q

Why isn’t Alpha radiation used in tracers

A

As it can only pass through a thin sheet of paper so the radiation would not be able to pass through the body into the surroundings

50
Q

How is radiation used in thickness gauges for materials such as foil/paper

A

Radiation is absorbed when passing through materials
1- If a material is too thick - more beta particles are absorbed and less are picked up by the tracer sending a signal to the rollers to increase the force on the material, making it thinner.
2- If material is too thin - less beta particles are absorbed and more are picked up by the tracer sending a signal to reduce the force on the material making it thicker

51
Q

How is radiation used in smoke alarms

A

Americium-241 is found in smoke alarms (alpha emitter)
Alpha particles ionise air particles making them charged and forms a current
Smoke entering the detector will be absorbed which stops the current and triggers the alarm

52
Q

How is radiation used within irradiating food

A

Gamma rays (colbalt-60) are emitted onto food to destroy any bacteria and increasing shelf life

53
Q

How is radiation used to treat cancerous cells

A

Beams of gamma ray (a.k.a gamma knife) are aimed at the tumour at different angles to maximise the dose without harming healthy tissue

54
Q

How is radioactive materials used for sterilising material

A

Irradiating the equipment kills any living organisms, preventing pathogens from being transferred

55
Q

Why are gamma rays the best for irradiating food

A

It’s the most penetrating

56
Q

How can ionising rays cause cancer

A

Atoms exposed to radiation either die or break within the DNA - wrong reformation could lead to mutations which if replicated can cause cancer

57
Q

How do ionising rays cause tissue damage

A

High energy rays such as gamma and x-ray can cause the damage of healthy tissue during treatments

58
Q

What are 2 safety measures that can be taken when using radiation in medicine

A

1- Use radioactive material with a short half-life which can be quickly removed after a day
2- isolate them from the radioactive material as every-day exposure can cause cancer

59
Q

What is contamination (short-lasting or long-lasting?)

A

Longlasting: The source of radiation is transferred towards an object

60
Q

What is irradiation (short-lasting or long-lasting?)

A

Shortlasting: A source emits radiation which reaches an object

61
Q

How are tumours treated using internal radiotherapy

A

Small pellets of radioactive materials are inserted into a tumour

62
Q

How are radioactive substances used in PET scanners

A

1- Radioactive tracers are tagged to the desired chemical
2- When inserted the tracer travels to where the chemical is usually located
3- The radioactive atom on tracer loses radioactivity producing a positron
4- The positron hits an electron at high speeds they combine and destroy emitting gamma rays in opposite directions
5- PET scan records from the different angles where the racer is and produces a 3D image

63
Q

Why do the isotopes in PET scanners have to be produced nearby

A

As they contain a half time of 110mins

64
Q

What are 3 advantages of nuclear power stations

A
  1. Doesn’t produce carbon dioxide
  2. Low fuel cost and quantity
  3. Long lifetime
65
Q

What are 2 disadvantages of nuclear power stations

A
  1. Waste is radioactive and difficult to dispose
  2. Large-scale accidents are catastrophic
66
Q

What is nuclear fusion

A

the process of small nuclei being forced together (under immense temperature and pressure) to form a heavier nucleus

67
Q

Why does fusion happen at such high pressures and temperatures

A

To overcome the electrostatic repulsion

68
Q

What is fission

A

The splitting up of large and unstable nuclei into smaller nuclei

69
Q

What are the steps of fission of Uranium-235

A

1- Unstable nucleus of 235 absorbs 2 more neutrons causing it to be less stable
2- As a result it splits apart into daughter nuclei releasing energy in gamma radiation and two more neutrons

70
Q

How does the nuclear reactions including fission and fusion produce energy

A

Fission - energy for power plants
Fusion - energy source for stars

71
Q

How do moderators control a chain reaction within a nuclear reactor

A

Graphite or Heavy water material that slows down the neutrons released from fission so that they cause more fission.

72
Q

How do control rods control a chain reaction within a nuclear reactor

A

Boron rods in the reactor core absorb excess neutrons to prevent a runaway chain reaction

73
Q

How does thermal energy from chain reactions get used to create electricity

A

Thermal energy from the reaction is absorbed by coolant (water) which then evaporates into steam. The steam is used to turn a turbine which is used to generate electricity.

Physics: paper 1 (6 decks)

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