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GCSE Physics (Advanced Specification 2022 ONLY) > P7 - Radioactivity > Flashcards

P7 - Radioactivity Flashcards

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1
Q

What is activity?

A

The number of unstable atoms that decay per second in a radioactive source

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2
Q

What is alpha radiation (α)

A

Alpha particles, each composed of 2 protons and 2 neutrons (helium nuclei), emitted by unstable nuclei at an extremely high speed

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3
Q

What is an atomic number?

A

The number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number

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4
Q

What is beta radiation (β)?

A

Beta particles that are high energy electrons created in, and emitted from, unstable nuclei

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5
Q

What is a chain reaction?

A

Reactions in which one reaction causes further reactions, which in turn cause further reactions, etc.

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6
Q

What is the count rate?

A

the number of decays recorded each second by a Geiger counter

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7
Q

What is gamma radiation (γ)?

A

Electromagnetic radiation emitted from unstable nuclei in radioactive substances

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8
Q

What is a half-life?

A

Average time taken for half the number of nuclei of the isotope (or mass of the isotope) in a sample to decay.

Average time for the count rate to fall by half

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9
Q

What is ionisation?

A

Any process in which atoms become charged (become ions)

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10
Q

What does irradiated mean?

A

Objects near a radioactive source are said to be irradiated by it. This simply means that they’re exposed to a radioactive source. This does not make the source radioactive.

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11
Q

What are isotopes?

A

Atoms with the same number of protons and different numbers of neutrons

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12
Q

What is radioactive contamination?

A

The unwanted presence of materials containing radioactive atoms on other materials. The contaminating atoms may then decay, releasing radiation which may cause harm. Contamination is especially dangerous as radioactive particles may get inside your body

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13
Q

How were radioactive materials discovered?

A

Henri Becquerel used covered photographic plates that were placed under uranium salts to discover radioactivity. Henri Becquerel’s work was expanded on by Marie and Pierre Curie, who investigated and discovered a range of new radioactive elements

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14
Q

What is radiation?

A

The emission of energy as electromagnetic waves or as moving subatomic particles

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15
Q

What is the unit for radioactivity (and count rate)?

A

Becquerels (Bq), where 1 Bq = 1 nuclear decay event per second

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16
Q

What type of substances emit radiation?

A

Substances containing atoms with unstable nuclei

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17
Q

What causes a nucleus to become unstable?

A
  • If it contains too many protons
  • If it contains too many neutrons
  • If it is too large

These factors cause the nucleus to have excess energy, making it unstable

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18
Q

Why does an unstable nuclei undergo nuclear decay/

A

An unstable nuclei can undergo nuclear decay, emitting radiation and becoming more stable as they do so.

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19
Q

What is a geiger counter?

A

A Geiger counter is a device that counts the number of radioactive particles per second. A Geiger counter clicks even when it is not near a radioactive source, this effect is due to background radiation

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20
Q

Why does a Geiger counter click even when it is not near a radioactive source?

A

Due to background radiation

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21
Q

What is a radioisotope?

A

An isotope which has an unstable nucleus. It will decay by emitting radiation

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22
Q

What is the difference between a daughter nucleus and the parent nucleus, when the parent nucleus has emitted alpha radiation?

A

The daughter nucleus would have an atomic mass of 4 less than the parent nucleus and an atomic number of 2 less than the parent nucleus

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23
Q

Write the equation for Thorium-232 decaying by emitting alpha-radiation (atomic number = 90)

A
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24
Q

Explain how Beta Decay occurs:

A

An atom decays into a new atom by changing a neutron into a proton and an electron. The fast moving, high energy electron is emitted and is known as a beta particle

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25
Q

What is the difference between a daughter nucleus and the parent nucleus, when the parent nucleus has emitted beta radiation?

A

The daughter nucleus would have the same atomic mass, but the atomic number would increase by 1.

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26
Q

Write the equation for Radium-228 decaying by emitting beta-radiation (atomic number = 88)

A
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27
Q

What is the difference between a daughter nucleus and the parent nucleus, when the parent nucleus has emitted gamma radiation?

A

There is no atomic change within the nucleus

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28
Q

Explain the process of gamma decay:

A

Gamma radiation is surplus energy sometimes emitted after alpha or beta decay. The atom itself is not changed. Gamma radiation is part of the EM spectrum; a wave with a very high frequency, very short wavelength

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29
Q

What type of wave is gamma radiation?

A

An electromagnetic wave with a very high frequency, very short wavelength

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30
Q

Write the equation for when Radon 224 decays by alpha emission:

A
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31
Q

Write the equation for when Strontium 90 decays by beta emission

A
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32
Q

What is 1 bequerel?

A

1 decay event per second

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33
Q

What is the symbol for alpha radiation?

A

α

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34
Q

What is the symbol for beta radiation?

A

β

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35
Q

What is the symbol for gamma radiation?

A

γ

36
Q

What is the range in air of alpha radiation?

A

5cm

37
Q

What is the range in air of beta radiation?

A

1 metre

38
Q

What is the range in air of gamma radiation?

A

unlimited - spreads out in air without being absorbed

39
Q

What is the penetrative power of alpha radiation?

A

It can be stopped by a sheet of paper / skin

40
Q

What is the penetrative power of beta radiation?

A

it can be stopped by 3mm of aluminium or a thin lead sheet

41
Q

What is the penetrative power of gamma radiation?

A

It can be stopped by a thick lead sheet (several cm thick) or concrete (more than 1m thick)

42
Q

What is the ionising power of alpha radiation?

A

Very strong ionising

43
Q

What is the ionising power of beta radiation?

A

relatively ionising, less ionising than alpha but more ionising than gamma

44
Q

What is the ionising power of gamma radiation?

A

Weakly ionising

45
Q

What is ionising power?

A

The ability for nuclear radiation to remove electrons from atoms to form ions

46
Q

Why is alpha radiation the most ionising?

A

Alpha particles are the most ionising because they have the largest mass and charge. Therefore they interact with the electrons most strongly. Gamma rays do not interact with electrons strongly at all

47
Q

What is the nuclear equation for alpha-decay?

A
48
Q

What is the nuclear equation for beta-decay?

A
49
Q

What happens to the activity of a source as more and more unstable atoms decay?

A

As there are fewer unstable atoms there is a lower activity as fewer unstable atoms decay per second

50
Q

Radioactive decay is …………………….., …………….., ………………….

A
  • Random / Spontaneous
  • Not effected by temperature
  • Unpredictable
51
Q

What is the half life of iodine-131?

A

8 days

52
Q

What is the equation for count rate after “n” half lives?

A

Count rate after “n” half lives = Count rate before / 2ⁿ

53
Q

What is the half life of carbon-14?

A

5760 years

54
Q

What is the isotope used in carbon dating and why?

A

Carbon-14 as it is a radioisotope and decays over time

55
Q

The half-life of a source of carbon-14 is 5760 years. After how many years will the number of radioactive particles be 12.5% of the original amount?

A

17280

56
Q

The half life of radon-222 is 3.8 days. If the original amount of this source was 2400 Bq, what do you expect it to be after 15.2 days?

A

150 Bq

57
Q

What radioisotope is used in radioactive tracers and why?

A

Iodine-131 is used because:

  • Its half life is eight days, so it lasts long enough for the test to be done, but decays almost completely after a few weeks
  • It emits gamma radiation, so it can be detected outside the body
  • It decays into a stable product
58
Q

Why is it not possible to know when a nucleus will decay?

A

Because nuclear decay is random and uncontrollable

59
Q

What is the activity of a radioactive material that emits 400,000 particles over a period of 20 minutes?

A

333.3 Bq

60
Q

Why does radioactive waste need to be stored securely and for many years?

A

To prevent radioactive contamination of the environment and it needs to be stored for many years as the waste contains radioisotopes with long half lives

61
Q

How is nuclear waste dealt with?

A

Used fuel rods are removed from a reactor and stored in big tanks of water for up to a year to cool down. Remote-control machines are then used to open up the fuel rods. The unused uranium and plutonium is removed chemically so that it can be reused. The material that is left contains lots of radioactive isotopes with long half lives. This radioactive waste has to be stored in secure conditions for many years to prevent radioactive contamination of the environment

62
Q

What does it mean if a substance is radioactive?

A

if the substance contains atoms that decay, releasing radiation in the form of particles or energy

63
Q

How do you reduce the effect of irradiation?

A
  • Keeping sources in a lead-lined box
  • Standing behind barriers or being in a different room
  • Using remote-controlled arms
64
Q

How do you reduce the effects / avoid radioactive contamination?

A
  • Gloves and tongs should be used when handling sources, to avoid particles getting stuck to your skin or under your nails
  • Using protective suits to stop particles being breathed in
65
Q

Is irradiation or contamination the main concern when working with alpha particle emitting sources?

A

Contamination, this is because alpha particles can only travel a few centimetres in the air and cannot penetrate your skin and cause damage to your internal organs but can cause great damage if already inside your body

66
Q

Explain the seriousness of irradiation and contamination outside the body:

A

Outside the body, beta and gamma sources are the most dangerous. This is because beta and gamma particles can penetrate the body and get to the delicate organs. Alpha is less dangerous because it cannot penetrate the skin and is easily blocked by a small air gap as it can only travel a few centimetres in the air. High levels of irradiation from all sources are dangerous, especially from beta and gamma emitting sources

67
Q

Explain the seriousness of irradiation and contamination inside the body:

A

Inside the body, alpha sources are the most dangerous, this is because they do all their damage in a very localised area. So contamination, rather than irradiation, is the main concern when working with alpha sources. Beta sources are less damaging inside the body, as radiation is absorbed over a wider area, and some passes out of the body all together. Gamma sources are the least dangerous inside the body, as they mostly pass straight out - they have the lowest ionising power

68
Q

What are the risks of irradiation?

A
  • Radiation can enter living cells and ionise atoms and molecules within them. This can lead to tissue damage
  • Lower doses tend to cause minor damage without killing the cells. This can cause mutations which cause the cells to divide uncontrollably. This is known as cancer
  • Higher doses tend to kill cells completely, causing radiation sickness (leading to vomiting, tiredness and hair loss) if a lot of cells all get irradiated at once
69
Q

How do unstable nuclei become stable?

A

Nuclear decay

70
Q

What is the mass, atomic number, and charge of an alpha particle?

A 
mass = 4
number = 2
charge = +2
71
Q

what is the mass and charge of a beta particle?

A 
mass = almost 0
charge = -1
72
Q

What is the equation for number of unstable nuclei after “n” half lives?

A

number of unstable nuclei after “n” half lives = initial number of unstable nuclei / 2ⁿ

73
Q

Why is a moderator needed to slow high-speed neutrons in a nuclear reactor?

A

slower moving neutrons are more effective in causing a fission event, faster moving neutrons don’t cause further fission

74
Q

How would workers who work with radioactive materials reduce risk of exposure to radiation?

A

Wear a personal radiation monitor, such as a film badge. This badge shows if it is over-exposed to ionising radiation, its wearer should not continue to work with radioactive equipment for a period of time

75
Q

What are 5 nuclear issues?

A
  • Background radiation
  • Nuclear waste
  • Nuclear accidents
  • Half-lives and instability
  • Radioactive risks
76
Q

What is heavy hydrogen?

A

Another term for the hydrogen isotope deuterium, it has a mass number of 3 (contains 1 proton and 2 neutrons)

77
Q

Explain how nuclear waste is a nuclear issue and how it is dealt with.

A

Used fuel rods are extremely hot and very radioactive. After they are removed from a reactor, they are stored in big tanks of water for up to a year. The water cools the rods down. Remote-control machines are then sued to open up the fuel rods. The unused uranium and plutonium are removed chemically from the used fuel. These are stored in sealed containers so they can be used again. The material that’s left contains lots of radioactive isotopes with long half-lives. This radioactive waste has to be stored in secure conditions for many years to prevent contamination of the environment

78
Q

Explain how nuclear accidents are a nuclear issue and how it is dealt with.

A

In 1986, a nuclear reactor in Ukraine exploded. A cloud of radioactive material from the fire drifted over many parts of Europe, including Britain. More than 100 000 people were evacuated and over 30 people died in the accident. More have developed leukaemia or other cancer types since then. The Chernobyl reactor did not have high-speed shutdown systems like most reactors have, safety instructions were ignored. Lessons learnt were put into place during the Fukushima meltdown, the population within 20km were evacuated and many things were monitored for years to come.

79
Q

Explain how the half life an instability of a nuclei is a nuclear issue:

A

Radioactive isotopes have a wide range of half-loves. Some radioactive isotopes have half-lives of a fraction of a second, whilst others have half-lives of over 1 billion years. Isotopes with the shortest half-lives have the most unstable nuclei - so they emit a lot of radiation in a short amount of time

80
Q

Why does the hazards caused by the ionising effect of radiation from radioactive materials decrease over time?

A

The half-life of a radioactive source tells you how quickly its activity decreases. As its activity decreases, the rate it gives out radiation decreases. So the hazards caused by the ionising effect of the radiation from radioactive materials decrease with time according to the half-lives of their isotopes.

81
Q

Why are gamma rays weakly ionising?

A

They do not interact with the atoms much, they tend to pass straight through

82
Q

Is it safe to eat irradiated food?

A

Yes, irradiating food does not make it radioactive, it simply kills the hsrmful bacteria and other pathogens that may be on the food

83
Q

Explain the process of nuclear fission:

A

An unstable and fissionable nucleus may absorb a neutron. This causes the nucleus to split into 2 daughter nuclei, releasing energy. It also releases 2 or 3 neutrons which may go onto cause further fission.

83
Q

Explain the process of nuclear fission:

A

An unstable and fissionable nucleus may absorb a neutron. This causes the nucleus to split into 2 daughter nuclei, releasing energy. It also releases 2 or 3 neutrons which may go onto cause further fission.

84
Q

In what form is energy released in nuclear fission?

A

Gamma rays

85
Q

How may neutrons are emitted in nuclear fission?

A

2 or 3 neutrons

GCSE Physics (Advanced Specification 2022 ONLY) (16 decks)

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