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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
What is an alpha particle?
Produced by alpha rays and alpha radiation. +2 charge
26
How far can alpha particles travel in air?
An inch
27
What can block alpha particles?
A sheet of paper
28
How ionising are alpha particles?
Highly
29
What are alpha particles used for?
Smoke detectors Treating cancer Projectiles
30
What are beta particles?
A fast moving electron emitted by radioactive decay of substances -1 charge
31
How far can beta particles travel on air?
Several yards
32
What can beta particles be stopped by?
Thin layer of aluminium or clothing
33
How ionising are beta particles?
Not as ionising as alpha particles
34
What are beta particles used for?
Treat cancer Tracers Prevent growth of certain tissues
35
What is a gamma ray?
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
How far can gamma rays travel in air?
Hundreds of metres
37
What can block gamma rays?
Lead
38
How penetrating are gamma rays?
They have so much penetrating power that they can damage DNA
39
What can gamma rays be used for?
Sterilise equipment Tracers Radio therapy
40
What is radioactivity?
Where an unstable nucleus changes its composition and emits alpha, beta or gamma radiation
41
What is an alpha particle?
A helium nucleus
42
How ionising are gamma rays?
Not very
43
What are activity and counter rate measured in?
Becquerels (Bq)
44
What happens in an alpha decay equation?
Loses 4 mass and 2 atomic number every time. Emits gamma radiation as well
45
What happens in a beta decay equation?
Gains one atomic number + gamma radiation + e- mass number 0, proton number -1
46
What happens during beta decay?
A neutron splits up into a proton and an electron.
47
What is the half life?
The time for half the atoms in a sample to decay
48
What is the equation for activity?
Initial activity x 0.5^number of half lives
49
What is background radiation?
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
What is radiation dose measured in?
Sieverts
51
What is nuclear fission?
The splitting of an atomic nucleus
52
What is induced fission?
Starts with a neutron
53
What is spontaneous fission?
Happens on its own
54
What is released in fission?
2 daughter nuclei, 3 neutrons, lots of energy
55
What is a chain reaction?
Neutrons released cause more fission
56
How do control rode control nuclear fission?
Absorb neutrons
57
In the sun what is nuclear fusion?
Hydrogen --> helium + energy
58
What is fusion in a nuclear reactor?
Heavy hydrogen --> helium + energy
59
What is fusion in a hydrogen bomb?
Uranium bomb surrounded by hydrogen
60
What happens in the sun?
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
What happens at short distances? (Nuclear force vs repulsive electrostatic force)
The attractive nuclear force is stronger than the repulsive electrostatic force
62
What is the main technical difficulty for fusion?
Getting the nuclei close en enough to fuse
63
Sun fusion facts
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
What happens during nuclear fission in a nuclear reactor?
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
What is an advantage of nuclear reactors?
Low cost once commissioned
66
What is a disadvantage of nuclear reactors?
Can cause large scale accidents
67
What is nuclear fusion?
Hydrogen atoms heated Fusion reaction Helium neutron and energy released Neutron energy heats water
68
What is irradiation?
When an object is exposed to nuclear radiation
69
What is contamination?
When atoms of a radioactive material are on or in an object
70
How can you protect from irradiation and contamination?
Maintaining a distance from the radiation source Limiting time near the source Shielding from the radiation

Physics (17 decks)

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