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Physics > P4 Radioactivity > Flashcards

P4 Radioactivity Flashcards

1
Q

Activity

A

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

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2
Q

Alpha radiation

A

alpha particles, each composed of two protons and two neutrons, emitted by unstable nuclei.

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3
Q

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

Background radiation

A

ionising radiation that is around us all the time from a number of sources. Some background radiation is naturally occurring, but some comes from human activities.

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5
Q

Beta radiation

A

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

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6
Q

Control rod

A

a rod that can be lowered into the core of a nuclear reactor, to absorb neutrons and slow down the nuclear chain reaction.

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7
Q

Cosmic rays

A

charged particles with a high energy that come from stars, neutron stars, black holes and supernovae.

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8
Q

Count rate

A

Count rate: the number of counts per second detected by a Geiger counter

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9
Q

Decay

A

when a radioactive isotope emits ionising radiation

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10
Q

Decommission

A

Dismantle safely

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11
Q

Fuel rod

A

a rod containing the nuclear fuel for a nuclear reactor.

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12
Q

Gamma radiation

A

electromagnetic radiation emitted from unstable nuclei in radioactive substances.

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13
Q

Geiger Muller tube

A

a device that can detect ionising radiation and is used to measure the activity of a radioactive source.

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14
Q

Half life

A

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

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15
Q

Ionisation

A

any process that in which atoms become charged.

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16
Q

Irradiated

A

an object has been exposed to ionising radiation.

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17
Q

Isotope

A

atoms with the same number of protons and different number of neutrons.

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18
Q

Mass number

A

the number of protons and neutrons in a nucleus.

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19
Q

Nuclear equation

A

an equation representing a change in an atomic nucleus due to radioactive decay. The atomic numbers and mass number must balance.

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20
Q

Random

A

any process that cannot be predicted and can happen at any time is said to be random.

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21
Q

Unstable

A

an unstable nucleus in an atom is one that will decay and give out ionising radiation.

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22
Q

When is light emitted from an atom?

A

When an electron falls down an energy level

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23
Q

What happens when an electromagnetic wave is absorbed by an atom?

A

An electron is promoted to a higher energy level

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24
Q

What is radioactivity?

A

Caused by nuclear changes. It is harmful and can cause burns or cancer. We are surrounded by it at a low level. Released by nuclear fuels.

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25
Q

What is an alpha particle?

A

Produced by alpha rays and alpha radiation. +2 charge

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26
Q

How far can alpha particles travel in air?

A

An inch

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27
Q

What can block alpha particles?

A

A sheet of paper

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28
Q

How ionising are alpha particles?

A

Highly

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29
Q

What are alpha particles used for?

A

Smoke detectors
Treating cancer
Projectiles

30
Q

What are beta particles?

A

A fast moving electron emitted by radioactive decay of substances -1 charge

31
Q

How far can beta particles travel on air?

A

Several yards

32
Q

What can beta particles be stopped by?

A

Thin layer of aluminium or clothing

33
Q

How ionising are beta particles?

A

Not as ionising as alpha particles

34
Q

What are beta particles used for?

A

Treat cancer
Tracers
Prevent growth of certain tissues

35
Q

What is a gamma ray?

A

Penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength of the electromagnetic spectrum. No charge.

36
Q

How far can gamma rays travel in air?

A

Hundreds of metres

37
Q

What can block gamma rays?

A

Lead

38
Q

How penetrating are gamma rays?

A

They have so much penetrating power that they can damage DNA

39
Q

What can gamma rays be used for?

A

Sterilise equipment
Tracers
Radio therapy

40
Q

What is radioactivity?

A

Where an unstable nucleus changes its composition and emits alpha, beta or gamma radiation

41
Q

What is an alpha particle?

A

A helium nucleus

42
Q

How ionising are gamma rays?

A

Not very

43
Q

What are activity and counter rate measured in?

A

Becquerels (Bq)

44
Q

What happens in an alpha decay equation?

A

Loses 4 mass and 2 atomic number every time. Emits gamma radiation as well

45
Q

What happens in a beta decay equation?

A

Gains one atomic number + gamma radiation + e- mass number 0, proton number -1

46
Q

What happens during beta decay?

A

A neutron splits up into a proton and an electron.

47
Q

What is the half life?

A

The time for half the atoms in a sample to decay

48
Q

What is the equation for activity?

A

Initial activity x 0.5^number of half lives

49
Q

What is background radiation?

A

Comes from natural sources such as rocks and cosmic rays and man made sources such as nuclear accidents. Always around us. May be affected by occupation/ location.

50
Q

What is radiation dose measured in?

A

Sieverts

51
Q

What is nuclear fission?

A

The splitting of an atomic nucleus

52
Q

What is induced fission?

A

Starts with a neutron

53
Q

What is spontaneous fission?

A

Happens on its own

54
Q

What is released in fission?

A

2 daughter nuclei, 3 neutrons, lots of energy

55
Q

What is a chain reaction?

A

Neutrons released cause more fission

56
Q

How do control rode control nuclear fission?

A

Absorb neutrons

57
Q

In the sun what is nuclear fusion?

A

Hydrogen –> helium + energy

58
Q

What is fusion in a nuclear reactor?

A

Heavy hydrogen –> helium + energy

59
Q

What is fusion in a hydrogen bomb?

A

Uranium bomb surrounded by hydrogen

60
Q

What happens in the sun?

A

2 protons (hydrogen nuclei) fuse making heavy hydrogen nucleus and positron (one proton has changed to a neutron)
Positron - same size as an electron but opposite charge.
Another protons hits heavy hydrogen to make heavier nucleus (a lighter form of helium 3 2) 2 lots of lighter helium collide to make a normal helium nucleus + 2 protons + energy

61
Q

What happens at short distances? (Nuclear force vs repulsive electrostatic force)

A

The attractive nuclear force is stronger than the repulsive electrostatic force

62
Q

What is the main technical difficulty for fusion?

A

Getting the nuclei close en enough to fuse

63
Q

Sun fusion facts

A

75% hydrogen, 25% helium, slowly changing to more helium
Sun is a plasma of bars nuclei with no electrons
Energy given out if colliding nuclei are no bigger than iron
To fuse bigger nuclei, have to put in energy

64
Q

What happens during nuclear fission in a nuclear reactor?

A

A neutron collides with a uranium atom, releasing 2 daughter nuclei, 3 neutrons and lots of energy as gamma rays. Some neutrons are absorbed by control rods to keep control.

65
Q

What is an advantage of nuclear reactors?

A

Low cost once commissioned

66
Q

What is a disadvantage of nuclear reactors?

A

Can cause large scale accidents

67
Q

What is nuclear fusion?

A

Hydrogen atoms heated
Fusion reaction
Helium neutron and energy released
Neutron energy heats water

68
Q

What is irradiation?

A

When an object is exposed to nuclear radiation

69
Q

What is contamination?

A

When atoms of a radioactive material are on or in an object

70
Q

How can you protect from irradiation and contamination?

A

Maintaining a distance from the radiation source
Limiting time near the source
Shielding from the radiation

Physics (17 decks)

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