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Physics OCR > Radioactivity * > Flashcards

Radioactivity * Flashcards

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1
Q

What is the number of protons equal to?

A

the number of electrons

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2
Q

What is the atomic number?

A

the number of protons

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3
Q

What is the mass number?

A

the number of protons and neutrons

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4
Q

Which number is at the top of the element on the periodic table and which is on the bottom?

A

mass number (bigger number) is at the top and the atomic number is at the bottom

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5
Q

What was Rutherfords gold foil experiment?

A

he fired a beam of alpha particles at a sheet of gold foil

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6
Q

What were the three conclusions of the gold foil experiment?

A

1) most particles passed through - shows that most of an atom is empty space
2) a few particles rebounded - shows that an atom contains a tiny, dense nucleus
3) some particles passed through but were deflected in a different direction - shows that the positive alpha particles were repelled by the positive charge of the nucleus

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7
Q

What is alpha decay?

A

when an alpha particle is emitted from the nucleus of an atom

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8
Q

What is an alpha particle?

A

2 protons and 2 neutrons

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9
Q

What charge and mass do alpha particles have?

A

+2 charge and a mass of 4

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10
Q

What happens to the element when an alpha particle is emitted?

A

the element changes - the mass number decreases by 4 and the atomic number decreases by 2

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11
Q

What are the ionising and penetrating powers of alpha decay?

A

its highly ionising but weakly penetrating

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12
Q

What are alpha particles stopped by?

A

a sheet of paper

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13
Q

What is beta minus decay?

A

when a neutron turns into a proton, and a beta minus particle is released by the nucleus

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14
Q

What is a beta minus particle?

A

an electron

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15
Q

What happens to the element when a beta minus particle is emitted?

A

the element changes - the mass number stays the same but the atomic number goes up by 1

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16
Q

What are the ionising and penetrating powers of beta minus decay?

A

medium ionising power and medium penetrating power

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17
Q

What are beta minus patricles stopped by?

A

a few mm of aluminium

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18
Q

What is beta plus decay?

A

when a proton changes into a neutron and a beta plus particle is released by the nucleus

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19
Q

What is a beta plus particle?

A

a positron

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20
Q

What happens to the element when a beta plus particle is released?

A

the element changes - the mass number stays the same and the atomic number decreases by 1

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21
Q

What is gamma decay?

A

when a gamma ray is emitted by the nucleus to get rid of energy to become more stable

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22
Q

What is a gamma ray?

A

an electromagnetic wave that has no mass or charge

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23
Q

What happens to the element when a gamma ray has been emitted?

A

it stays the same - gamma rays have no mass and no charge

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24
Q

What are the ionising and penetrating powers of gamma rays?

A

its weakly ionising and highly penetrating

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25
Q

What is gamma radiation stopped by?

A

thick lead or concrete

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26
Q

What is neutron emission?

A

when the nucleus emits a neutron

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27
Q

What happens to the element when a neutron is emitted?

A

the element changes - the mass number decreases by 1 and the atomic number stays the same

28
Q

What happens to the nucleus after a neutron has been emitted?

A

the nucleus because a different isotope of the element

29
Q

What is background radiation?

A

low level ionising radiation that is present at all times

30
Q

What is activity?

A

the number of nuclei that decay per second

31
Q

What is activity measured in?

A

Bequerels (Bq)

32
Q

How do you calculate activity?

A

activity = counts / time

33
Q

Give three sources of background radiation

A
  • nuclear power and weapons
  • medical sources
  • food and drink
34
Q

What is ionising radiation?

A

radiation that has enough energy to knock electrons off of atoms

35
Q

What is ionisation?

A

the gaining or losing of an electron

36
Q

How is background radiation measured?

A

using a geiger-muller counter

37
Q

How is background radiation detected?

A

using a geiger-muller tube or photographic film

38
Q

What is half life?

A

the time taken for half the unstable nuclei in a sample of a radioactive isotope to decay

39
Q

Give four uses of ionising radiation

A

smoke alarms, radiotherapy, PET scans, medical tracers

40
Q

Which kind of radiation is used in smoke alarms?

A

alpha

41
Q

Which kind of radiation is used in radiotherapy?

A

ionising radiation - usually gamma or alpha

42
Q

Which kind of radiation is used in PET scans?

A

beta plus

43
Q

Which kind of radiation is used in medical tracers?

A

gamma

44
Q

What are the dangers of very low radiation?

A

can enter living cells and cause ionisation which can lead to tissue damage

45
Q

What are the dangers of low radiation?

A

damages cells without killing them which can cause mutations leading to cancerous cells which divide forming a tumour

46
Q

What are the dangers of high radiation?

A

kills cells completely causing radiation sickness which causes vomiting, tiredness and hair loss

47
Q

What is irradiation?

A

radiation from a source that reaches your body (including background radiation)

48
Q

Give two precautions people working with radioactivity can take

A
  • staying out of range
  • protective clothing
49
Q

What is contamination?

A

radioactive substances or atoms that get into your body (this can happen if you touch a source)

50
Q

Why is contamination so dangerous?

A

these atoms will continue to decay producing ionising radiation, even when the source is removed

51
Q

What precautions can be taken to avoid contamination? (3)

A
  • gloves and tongs used when handling radioactive sources
  • protective suits to prevent contamination through breathing particles or getting any on the clothes or skin
  • radioactive sources used in medicine need to have appropriate half lives to reduce damage to the patients body
52
Q

What is nuclear fission?

A

a process in which energy is released from the nucleus of atoms as they are split

53
Q

The process of nuclear fission:

Fill the gaps:

  • a _______ is fired at a uranium235 ______
  • the ______ absorbs the ______, turning it into Uranium236 and making it more _______
  • the ______ splits in half into two daughter nuclei - _______ and ______
  • ______ is produced and 2 or 3 ______ are released from the ______
A
  • a neutron is fired at a uranium235 nucleus
  • the nucleus absorbs the neutron, turning it into Uranium236 and making it more unstable
  • the nucleus splits in half into two daughter nuclei - Krypton and Barium
  • energy is produced and 2 or 3 neutrons are released from the nucleus
54
Q

What is a chain reaction in nuclear fission?

A

a process where the products from nuclear fission causes further nuclei to split
this can get out of control because each splitting of a nucleus causes more nuclei to split

55
Q

What does the control rod do inside a nuclear reactor?

A

its placed between the fuel rods and is raised and lowered into the reactor to control the chain reaction - the control rods absorb the excess neutrons
usually made of boron

56
Q

What does the moderator do inside a nuclear reactor?

A

it slows down the neutrons which allows more reactions to take place
usually made of graphite

57
Q

What does the fuel rod do inside a nuclear reactor?

A

its made of uranium nuclei and captures slow moving thermal neutrons

58
Q

What does the shielding do inside a nuclear reactor?

A

it prevents the radioactive substances from getting out

59
Q

What is nuclear fusion?

A

the process of joining two nuclei to form a nucleus

60
Q

What happens in nuclear fusion?

A

two hydrogen atoms (one lighter and one heavier) are combined to form helium, which produces energy

61
Q

What conditions are needed for nuclear fusion?

A

extremely high pressures and temperatures - because the positively charged nuclei need to be very close to fuse so a lot of energy is needed to overcome the strong force of electrostatic repulsion

62
Q

How does nuclear fusion produce energy?

A

some of the mass of the lighter nuclei before fusion is converted into energy during fusion

63
Q

How is the energy released in nuclear fusion?

A

by radiation

64
Q

Where does nuclear fusion naturally occur?

A

in the sun

65
Q

What is a pro of nuclear fission and nuclear fusion

A

pro of nuclear fission - more energy is produced than is needed

pro of nuclear fusion - lots of hydrogen is available from water

66
Q

What are the practical issues of nuclear fusion?

A

a lot of energy is needed to achieve the high pressures and temperatures - this is expensive too

67
Q

Give two pros and cons of nuclear power (fission)

A

pros :

  • reliable alternative to fossil fuels - doesn’t produce CO2
  • huge amounts of energy can be generated

cons :

  • risk of radioactive leaks and explosions from power stations
  • waste products have a very long half life and may not be disposed of safely

Physics OCR (14 decks)

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