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Radioactivity Flashcards

(68 cards)

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1
Q

Rutherford’ gold and alpha particle experiment

A

Most went through proving that most of an atom is empty space. Some repelled (bounced back or small deflection). This showed that, because the alpha particles are positively charged, the nucleus is also positively charged due to repulsion

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2
Q

Nucleon

A

Proton or neutron

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3
Q

When and why do electrons change orbit?

A

When there is absorption or emission of electromagnetic radiation.
They are given energy either by heat or electricity and move up an energy level, moving further away from the nucleus. Electromagnetic waves are given off, transferring energy. Electrons are also given energy by being hit by electromagnetic rays

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4
Q

Emission spectra

A

Show how electrons can only be in certain orbits

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5
Q

Ionisation

A

When electrons leave an atom due to there being no more energy levels, and leave behind an ion

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6
Q

Alpha

A

2 protons and 2 electrons (helium) charge of 2+

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7
Q

Beta-

A

A fast moving electron. Charge if 1-1

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8
Q

Beta +

A

Positron. Charge of +1

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9
Q

Gamma

A

High frequency electromagnetic wave. Neutral charge

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10
Q

How are alpha, beta, neutron and gamma radiation emitted?

A

From unstable nuclei in a random process

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11
Q

Radiation

A

Energy that is emitted from a source

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12
Q

Nuclear

A

Radiation that is emitted from the nucleus of an atom

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13
Q

How do electrons change orbit

A

When they get given energy (electricity, heat or EM waves) they get excited and move away from the nucleus by moving to the next shells. The closer to the nucleus, the more stable they are and less energy they have (larger atomic radii). When they move back down energy levels, they give off visible light. If the energy is high enough, the electrons leave the atom, making it an ion with a positive charge

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14
Q

Ionising radiations

A

Alpha, beta -, beta + and gamma

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15
Q

Deuterium

A

Heavy hydrogen

2/1 H

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16
Q

Background radiation

A

Radioactivity is a natural occurrence so we are exposed to nuclear radiation all the time

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17
Q

Sources of radiation (6)

A

Space (cosmic), medical use, food, nuclear power, buildings/ground, radon gas

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18
Q

Geiger-Müller tube

A

Detects when the gas inside the chamber is ionised by radiation

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19
Q

Photographic film

A

Gets darker when exposed to radiation

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20
Q

Beta minus decay

A

A neutron turns into a proton and an electron. The proton stays but the electron gets thrown out

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21
Q

Beta plus decay

A

A proton turns into a neutron and a positron

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22
Q

Gamma decay

A

Protons and neutrons rearrange themselves (nuclear rearrangement) which releases energy

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23
Q

Stopping power

A

The minimum material needed to stop radiation
Alpha - cm of air, skin, paper
Beta - mm of aluminium
Gamma - cm of lead, m of concrete

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24
Q

Decay

A

The process of ejecting radiation

Measured in Bq Becquerel

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25
Half life
Time taken for half the radioactive nuclei to decay
26
What does half life enable people to do
Half life enables the activity of a large number of nuclei to be predicted during the decay process. We can predict when the substance will be safe
27
Dangers of radiation
Tissue/cell damage, cancer and death (due to ions in DNA causing mutations)
28
Dangers of radiation (more detail)
Alpha and beta particles can ionise atoms by attracting electrons in alpha or repelling them in beta. Ions in DNA can cause mutations which leads to cell damage and death or cancer
29
Calculate half life from graphs
Choose a value of activity that is easy to half, on the line of best fit. Record the time when the activity was at this level. Find when the activity has halved on the line of best fit and record the time. The half life is the difference between these two times. 1/2^number of half-lives x original number of nuclei = number of undecayed nuclei left
30
Precautions needed to reduce dangers
Don't come into contact (ionising causing mutation in DNA and damaging skin cells), use goggles and wear gloves (research labs and hospitals), use tongs, keep the radioactive substances in lead lined containers (because it is dense and it's the minimum stopping power for gamma). These are aimed at preventing contamination and limiting irradiation
31
Irradiation
When someone is exposed to radiation (alpha, beta or gamma) from a nearby source
32
Contamination
When someone gets particles of a radioactive source on themselves or inside their body
33
Difference between contamination and irradiation
Irradiation will stop when the person moves away, contamination stops when the source finishes decaying. Irradiation is outside, contamination is in. Irradiation doesn't cause the object to become radioactive, contamination does. Irradiation can be blocked, contamination can't be stopped
34
Advantages of contamination
Radioisotopes can be used as medical and industrial tracers. Isotopes with a short half-life means exposure can be limited. Imaging can replace some invasive surgical procedures
35
Disadvantages of contamination
Radioisotopes might go to places where they are not wanted. It can be difficult to ensure that all contaminants are removed (some may be left behind). Exposure can potentially damage healthy cells
36
Dangers of microwaves
Internal heating of body cells
37
Calculate number of undecayed nuclei left
1/2(to the power of number of half lives) x original number of nuclei
38
Dangers of infrared
Surface skin burns
39
Dangers of visible light
Eye damage
40
Dangers of ultra violet
Damage to surface cells and eyes, skin cancer and eye damage
41
Dangers of x rays and gamma
Cell mutation, tissue damage, cancer
42
Uses of radio waves
Radio broadcasting, satellite communications
43
Uses of microwaves
Cooking, satellite transmissions
44
Uses of infrared
Thermal imaging, optical fibres, security cameras, mobile phones, remote controls
45
Uses of visible light
Photography, illuminations
46
Uses of ultraviolet
Security marking, fluorescent lamps, detecting forged bank notes, disinfecting water
47
Uses of x rays
Medical x rays, airport security scanners
48
Uses of gamma and how it works
Sterilising food and medical equipment. - kills/destroys microbes, doesn't involve high temperatures so fresh fruit and plastic instruments can still be used without being damaged, it needs a strong emitter with a long half-life so that it doesn't need replacing too often. Detection of cancer and its treatment. - high doses kills living cells, directed to cancerous cells and tumours rather than the healthy cells. Detecting leaks - gamma emitting tracers used in industry, water supplies contaminated with radioisotope, leak causes a build-up of gamma emissions in that area, these are detected using a Geiger-Muller tube to find the exact point of the leak.
49
Uses of alpha and how it works
Smoke alarms/detectors. Alpha particles are easily absorbed. A weak source of alpha radiation e.g. Americium-242, is placed in the smoke detector, close to two electrodes. A source causes ionisation, giving a charge, and a current flows. A smoke alarm measures the movement of alpha particles across a small gap. If smoke enters, it will absorb the alpha radiation and the current will stop / a drop will be detected, triggering the alarm to sound
50
People who work in settings with radioactive sources
Research scientists, science teachers, industrial workers, medical staff and power station employees
51
Protecting people who work with radiation
Film or ring badges monitor the amount they are exposed to
52
PET scans
Positron emitting topography. They use radioisotope tracers such as fluorine-18 as the carrier molecule. (It is a form of glucose which is useful as it can be used in all parts of the body in respiration and is particularly important to explore the brain and heart. It is absorbed by tissues meaning, if a tumour is present, it will absorb more). It is injected into the patient's blood. The isotopes will emit positrons. When a positron and electron meet, they annihilate and two gamma rays are given off in opposite directions. The ring detector detects these rays and can locate the exact location of the tumour and multiple images are taken, creating a 3D image to be analysed by computers
53
Radioactive tracer
Used to investigate a patient's body without the need for invasive surgery
54
Problems with PET scans
The half-lives of radioisotopes are very short. This means that they often have to be produced in the hospitals or in a nearby location. The isotope must also be beta or gamma and not alpha so that the radiation can pass out the body (alpha is stopped by skin)
55
Uses of beta plus and how it works
PET scans. The positron and electron are attracted to each other. They meet and annihilate each other completely. This gives off energy in the form of two gamma rays in opposite directions
56
Uses of beta minus and how it works
Regulating paper thickness. Radiation is absorbed as it passes through materials. This allows it to gauge the thickness of paper by measuring the amount of radiation passed through. Beta particles are directed through the paper with a detector on the other side connected to a control unit. If the paper is too thick, more beta particles are absorbed and less are detected causing the control unit to adjust the rollers to give the correct thickness by making it thinner
57
Positron
And anti-electron. It has the same mass but opposite charge
58
Internal radiotherapy
This is rarer. The source of radiation is inside the patient. A radioactive beta emitter, usually iodine-131, is used. It is
59
Nuclear fission def
When a large atom splits into two smaller atoms. It is induced by a neutron. It is used to release energy from uranium or plutonium atoms
60
Nuclear fission process
A slow moving incident neutron meets a parent nucleus (uranium isotope — uranium-235). It splits it into two lighter daughter nuclei (new elements) and some neutrons, releasing thermal energy. These neutrons are now able to split other nuclei (not atoms) causing a chain reaction
61
How is fission used in nuclear power stations?
The nuclear energy released from fission is used to heat water. The steam turns a turbine which is connected to a generator (coil of wire) and generates electricity and sent to the national grid via transformers
62
Energy transfers in nuclear fission poster stations
Nuclear -> heat -> kinetic -> electrical
63
Main ways to control nuclear fission reactions
Control rod, coolant and moderator. If the chain reaction is uncontrolled it will release a large amount of energy really quickly like in an atomic bomb
64
Control rods
Substances that can absorb neutrons e.g. boron They can be raised or lowered depending on the rate of fission (less -> raise, more -> lower). They control the rate of fission and therefore control the chain reaction
65
Moderators
Slows the fast moving neutrons down so they can be captured by the uranium fuel rods e.g. water. This creates a steady rate of nuclear fission where one new neutron produces one new fission
66
How is nuclear waste dealt with and why is it a problem?
Fission has radioactive waste products that are difficult to dispose. They can't all be recycled to create more electricity. They have very long half lives. At the moment, they are dealt with by vitrification where the waste is melted with other materials to make glass. The liquid glass is then sealed inside steel canisters and buried underground. Another way is by putting it in thick metal containers and filling the hole with concrete. The main thing is to make sure there are plenty materials to absorb the radiation before it can reach Earth's surface
67
Nuclear fusion def
Joining two light, small nuclei together to create a larger nucleus and release energy
68
How is fusion better than fission?
Fusion releases lots more energy than fission for a given mass. It doesn't leave behind a lot of radioactive waste. There is already plenty of hydrogen present to use as a fuel

Physics (12 decks)

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