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Radioactivity + Magnetism Flashcards

1
Q

What are atoms made of?

A

Atoms consist of a tiny central nucleus surrounded by negatively charged electrons whizzing around in electron orbitals.

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2
Q

What is the nucleus of an atom made of?

A

The nucleus is made up of positive protons and neutral neutrons.

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3
Q

What does the atomic number of an atom tell you?

A

The atomic number tells you the number of protons in the nucleus.

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4
Q

What does the mass number of an atom tell you?

A

The mass number tells you the total number of protons and neutrons.

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5
Q

What are isotopes?

A

Isotopes are atoms of an element with the same number of protons but a different number of neutrons in their nucleus.

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6
Q

Do isotopes have the same atomic number?

A

Yes they have the same atomic number but different mass numbers.

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7
Q

What is an example of isotopes in carbon?

A

Carbon exists in a few different isotopes which all have six protons but different numbers of neutrons.

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8
Q

How many neutrons does carbon 12 have?

A

Carbon 12 has six neutrons.

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9
Q

How many neutrons does carbon 13 have?

A

Carbon 13 has seven neutrons.

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10
Q

How many neutrons does carbon 14 have?

A

Carbon 14 has eight neutrons.

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11
Q

How do we show the mass and atomic numbers of isotopes?

A

We write each number beside the chemical symbol with the mass number on top and the atomic number below.

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12
Q

What makes an atom unstable and prone to decay?

A

An unbalanced number of protons and neutrons makes atoms unstable and prone to radioactive decay.

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13
Q

What is radioactive decay?

A

Radioactive decay is when an unstable atom breaks down and emits radiation.

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14
Q

Why do unstable nuclei emit radiation?

A

Unstable nuclei emit radioactive particles to become more stable.

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15
Q

What does radiation do to other atoms?

A

Radiation causes ionisation by hitting other atoms and knocking electrons off them.

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16
Q

Why is radiation dangerous?

A

Radiation is dangerous because it knocks electrons from atoms in human cells resulting in damage to living tissue.

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17
Q

What are alpha particles made of?

A

Alpha particles are made up of two protons and two neutrons so they are identical to the nucleus of a helium atom.

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18
Q

Why are alpha particles highly ionising?

A

Alpha particles are fairly big and more likely to bump into other particles and knock electrons from them.

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19
Q

How far can alpha particles travel?

A

Alpha particles cannot travel very far which makes them weakly penetrating.

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20
Q

What can block alpha particles?

A

Alpha particles are blocked by paper skin or a few centimetres of air.

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21
Q

What is the charge of an alpha particle?

A

Alpha particles have a charge of plus 2 because they contain two protons.

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22
Q

Can alpha particles be deflected by an electric field?

A

Yes the negative electrons in the field attract the positive alpha particles and deflect them.

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23
Q

What happens to the mass and atomic number when an alpha particle is emitted?

A

The mass number decreases by 4 and the atomic number decreases by 2.

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24
Q

What is a beta particle?

A

A beta particle is an electron emitted from an atom when a neutron turns into a proton.

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25
Why are beta particles more penetrating than alpha particles?
Beta particles are lighter so they can travel further and are moderately penetrating.
26
What can beta particles pass through?
Beta particles can travel through paper but are blocked by thin metal such as aluminium.
27
How ionising are beta particles?
Beta particles are moderately ionising because they are smaller and collide with fewer atoms than alpha particles.
28
What is the charge of a beta particle?
Beta particles have a charge of minus 1.
29
How do beta particles behave in an electric field?
They are deflected away due to repulsion between the negative beta particle and the electrons.
30
What happens to the mass and atomic number when a beta particle is emitted?
The mass number stays the same and the atomic number increases by 1.
31
What is gamma radiation?
Gamma radiation is energy in the form of an electromagnetic wave with no particles emitted.
32
When does gamma radiation occur?
Gamma radiation occurs after alpha or beta decay when the nucleus has excess energy.
33
How does an atom get rid of excess energy after decay?
The atom emits a gamma ray to release the excess energy.
34
How penetrating is gamma radiation?
Gamma radiation is highly penetrating and can only be blocked by thick lead or concrete.
35
How ionising is gamma radiation?
Gamma rays are weakly ionising because they pass through substances without knocking off electrons.
36
What is the charge of gamma radiation?
Gamma radiation has no charge so it is not deflected by an electric field.
37
What happens to the mass number and atomic number when gamma radiation is emitted?
There is no change to the mass number or atomic number.
38
How can ionising radiation be detected?
Ionising radiation can be detected using a Geiger Muller tube or photographic film.
39
What does a Geiger Muller tube measure?
It measures the activity of a radioactive source by converting radioactive particles into a count rate.
40
Why should background radiation be measured?
To account for background radiation and improve accuracy in readings.
41
How should background radiation be measured?
Measure the background radiation three times and find the mean.
42
What should you do with the background radiation data?
Subtract the mean background radiation from all recorded data for radioactive sources.
43
What safety precautions should you take when handling a radioactive source?
Use tongs to handle the source and store it in a lead box when not in use.
44
How does photographic film detect radiation?
Photographic film turns darker the longer it is exposed to radiation.
45
Why do people who work with radiation wear badges with photographic film?
To monitor whether they are within the safe limits of radiation exposure.
46
What is background radiation?
Background radiation is weak radiation that can be detected from external sources.
47
What are the sources of background radiation?
The sources of background radiation can be natural or artificial.
48
What are some natural sources of background radiation?
Natural sources include cosmic rays radioactive rocks and plants that absorb radioactive minerals from the soil.
49
What are some artificial sources of background radiation?
Artificial sources include fallout from nuclear weapons testing medical sources and nuclear power plants.
50
What is the activity of a radioactive source?
The activity is the number of decays per unit time and is measured in becquerels.
51
Which would have a higher activity polonium or carbon 12?
Polonium would have a higher activity because it emits more ionising radiation in a given time.
52
Why does the activity of a radioactive source decrease over time?
Because fewer radioactive particles remain as more of the sample is emitted.
53
What is the half-life of a radioactive isotope?
The half-life is the time taken for half of the nucleus to decay or the time taken for the activity to halve.
54
How does the half-life differ between isotopes?
Different isotopes have different half-lives
55
How can we determine the half-life of a sample using a graph?
We can draw a line on the vertical axis where the activity of the sample is halved and read off the time from the horizontal axis.
56
What are alpha emitters with a long half-life used for?
They are used in smoke detectors where alpha particles travel across a small gap to a detector which produces an electric current.
57
What happens when smoke enters a fire alarm?
The smoke absorbs alpha particles causing a drop in the current which activates the alarm.
58
What are beta emitters used for in industry?
They are used to monitor the thickness of metal sheets by placing a source and a receiver on either side of the sheet.
59
How does a thickness monitoring system work?
The number of beta particles detected is proportional to the thickness and any change adjusts the rollers.
60
What are gamma emitters like technetium-99m used for?
They are used as tracers in medicine to check organ function by detecting the radiation as it moves through the body.
61
Why is the half-life of a gamma source important in medicine?
It must be long enough for the scan but short enough to limit radiation exposure to the patient.
62
What happens if a radioactive substance touches an object?
The object becomes contaminated as radioactive material is transferred to its surface.
63
What is irradiation?
Irradiation is when an object is exposed to radiation without being touched by the radioactive source.
64
How can food be sterilised using radiation?
Food is placed near a gamma source to kill microorganisms and make it safe to eat without becoming radioactive itself.
65
What happens when radiation hits human cells?
It can ionise molecules causing cell and tissue damage.
66
How can radiation cause cancer?
Ionisation can lead to DNA mutation which may cause the cell to divide uncontrollably and form a cancer.
67
Why must radioactive waste be disposed of carefully?
Some waste stays radioactive for thousands of years and must be stored safely to avoid leaks.
68
Why are earthquake zones unsuitable for radioactive waste disposal?
Movements from earthquakes could disturb storage and cause leakages.
69
Why might people oppose a local radioactive waste site?
Residents may not want to live near a radioactive dump site.
70
What happens when like poles are placed together?
Like poles repel.
71
What happens when opposite poles are placed together?
Opposite poles attract.
72
What type of force is magnetic force?
Magnetic force is a non-contact force.
73
What happens when opposite poles of two bar magnets are placed together?
A uniform magnetic field is created between them with straight parallel lines from north to south.
74
Which elements are magnetic?
Iron cobalt and nickel.
75
Is steel magnetic?
Yes because it contains iron.
76
What is a permanent magnet?
A permanent magnet is made of magnetic materials and always exerts a force on other magnets or magnetic materials.
77
What is an example of a permanent magnet?
A bar magnet.
78
Can the magnetism of a permanent magnet be turned on or off?
No it cannot.
79
What is a temporary magnet?
A temporary magnet only becomes magnetic when placed in a magnetic field and loses its magnetism when removed.
80
What is an example of a temporary magnet?
Soft iron.
81
Can a temporary magnet repel another magnet?
No it cannot.
82
How can you check if something is a permanent magnet?
By checking whether it can repel another magnet.
83
What is a magnetic field?
A magnetic field is the area around a magnet in which there is a magnetic force.
84
How can we represent the force exerted by a magnet?
We use magnetic field lines to represent the force exerted by a magnet.
85
What is a plotting compass?
A plotting compass contains a small magnet that aligns itself with a magnetic field.
86
What happens to iron filings when placed in a magnetic field?
Iron filings become induced magnets (temporary magnets).
87
How can magnetic field lines be drawn using a plotting compass?
By placing a bar magnet on a piece of paper and marking the direction the compass needle points, then repeating this at different places around the magnet and connecting the marks with lines.
88
How can magnetic field lines be drawn using iron filings?
By placing a bar magnet with some iron filings on a sheet of paper, and the filings will align with the magnetic field to form a clear pattern.
89
What do closer magnetic field lines indicate?
They indicate a stronger magnetic field.
90
What direction do magnetic field lines go?
They always go from North to South.
91
Do magnetic field lines ever overlap?
No

Physics (21 decks)

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