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PHYSICS FLASHCARDS: > 7 - RADIOACTIVITY AND PARTICLES > Flashcards

7 - RADIOACTIVITY AND PARTICLES Flashcards

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1
Q

Name the particles that make up and atom and state their electrical charges.

A

PROTON - POSITIVELY CHARGED
NEUTRON - NEUTRAL
ELECTRON - NEGATIVELY CHARGED

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2
Q

Describe the structure of the atom.

A

Made up of a positively charged nucleus, made up of protons and neutrons, and surrounded by negatively charged electrons orbiting the nucleus at different distances.

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3
Q

What is meant by an isotope of an element?

A

An isotope is the atom of the same element with the same atomic (proton) number, but different mass (neutron) number.

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4
Q

What is the atomic number, and what is the mass number?

A

Atomic Number - Number of protons.
Mass Number - Number of protons + neutrons.

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5
Q

What are the relative masses of a proton, neutron, electron?

A

Proton - 1
Neutron - 1
Electron - 1/1850

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6
Q

What is the relative charge of a proton?

A

1+

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7
Q

Why is an atom neutral?

A

An atom is neutral because it is made up of the same number of protons and electrons, and since protons are positively charged and electrons are negatively charged, it balances out to become neutral.

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8
Q

How does an atom become a positive ion.

A

An atom becomes a positive ion when electrons from the outer shell are lost. Since these are negatively charged, there are more positively charged ions (protons), than electrons, therefore creating a positively charged ion.

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9
Q

Name the types of ionising radiation?

A

Alpha
Beta
Gamma

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10
Q

What is meant by background radiation?

A

Background radiation is radiation in small amounts that usually occurs, and therefore has no major effect.

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11
Q

Describe sources of background radiation.

A

Rocks which give out radioactive radon gas.
Fallout from nuclear weapon testing.
Cosmic rays include high - energy charged particles penetrating the atmosphere.
Nuclear power plants with radioactive waste.
Medical sources such as x-rays from MRI scanners.

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12
Q

State two pieces of equipment used to detect background radiation.

A

Geiger - Miller Detector.
Photographic film.

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13
Q

Describe the process in which a Geiger miller detector works, to detect background radiation.

A

When the Geiger miller detector absorbs radiation it produces a pulse, which a machine uses to count the amount of radiation. The frequency of the pulse depends on the amount of radiation present. A high frequency of pulses would mean the tube is absorbing a large amount of radiation.

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14
Q

Describe the process in which photographic film works, to detect background radiation.

A

A photographic film turns dark when it absorbs radiation. This is useful for people who work on radiation, as the more radiation they are exposed to, the darker the film turns; therefore workers can realise when too much radiation is present.

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15
Q

Types of ionising radiation from least to most ionising.

A

GAMMA ———— > BETA ———— > ALPHA

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16
Q

Types of ionising radiation from least to most penetrating.

A

ALPHA ———— > BETA ———— > GAMMA

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17
Q

What is a gamma ray?

A

A high energy - carrying electromagnetic wave, from the electromagnetic spectrum.

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18
Q

Describe the process of beta decay?

A

A neutron splits into a proton and an electron, and an electron is emitted from the nucleus.

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19
Q

How does alpha decay affect the atomic and mass number of the atom?

A

ATOMIC NUMBER ———— > -2
MASS NUMBER ———— > -4

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20
Q

How does gamma radiation affect the atomic and mass number of an atom?

A

It doesn’t.

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21
Q

What effect does beta decay have on the atomic and mass number of an atom?

A

Mass number stays the same.
Atomic number increases since there is another proton added.

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22
Q

Why are gamma rays emitted in an atom?

A

When the nucleus decays, parts of the nucleus rearrange, and therefore some energy is left over. This energy has to be released somewhere, and is released via gamma rays.

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23
Q

How does the activity of a radioactive source decrease over a period of time?

A

It decreases exponentially, and decreased by a constant ratio, over constant time periods. E.G. every 10 mins a sample of radioactive substance might decrease quarterly.

24
Q

What does half life of a radioactive source mean?

A

Half-life is the time taken for a source to have half of its initial mass to decay. (Time taken for activity to drop to half of initial activity.)

25
Q

What is the unit of activity?

A

Becquerel (BQ)

26
Q

Can you predict when a nucleus will decay?

A

No, it is a random process.

27
Q

How do smoke alarms work?

A

A smoke alarm measures the movement of alpha particles across a small gap. If smoke enters the detector, it will absorb the alpha particles, and the detector will measure a drop in the number getting across the gap. This drop in measurement causes the alarm to sound.

28
Q

How is radiation used in medicine?

A

To sterilise equipment: gamma rays can kill bacteria cells.
Radiotheapy: To help treat cancer, high doses of radiation are directed at cancer cells.

29
Q

Role of beta radiation in tracers?

A

A medical tracer is placed into the body, and is connected to a computer. When beta radiation is detected it shows up on the computer, to produce an image.

30
Q

How is beta radiation used to detect thickness?

A

A beta source is placed above the material; a detector is placed beneath it. If a lot of radiation is detected(by the detector), too much radiation is passing through the material; it is therefore too thin. If only a little radiation is detected, the material blocks out too much radiation, and is too thick.

31
Q

Why is ionising radiation dangerous?

A

It can damage tissue and kill cells.
It can cause cell mutations.

32
Q

What precautions when dealing with ionising radiation?

A

Avoid handling source directly. (Use tongs)
Wear radiation protective clothing.
Keep the radiation in lead containers to reduce amount of radiation that can escape.
Avoid being exposed to radiation for extended periods of time.

33
Q

Does a long half-life, or short half-life make a radioactive source more dangerous.

A

A long half-life makes a radioactive source more dangerous, as it means the source will be highly radioactive for longer; it is therefore more dangerous.

34
Q

What precautions are taken for medical use of ionisation.

A

Only a small does is given to patients so they are not exposed to too much.
The radiation used has an extremely short half life, it won’t therefore be highly radioactive for long. Reduced risk for patients and doctors. Medical staff also wear protective clothing.

35
Q

Difference between contamination and irradiation?

A

Contamination is when radioactive substances are transferred to objects through processes such as touching the source/ breathing it in.
Irradiation is when the object comes in contact with the radioactive source. The source doesn’t actually enter your body, and the radiation will stop if you move away from the area.

36
Q

Differences between treating tumors internally and externally?

A

Both methods try to target specific cells, however surrounding healthy tissue is also damaged. Internal method uses a tracer, and uses alpha radiation, which is poorly penetrating and cannot reach the healthy cells. External method uses a beam, that concentrates on specific parts of the body. For external method a long half-life is required, but for internal method a short half-life is required so it doesn’t remain in body for too long.

37
Q

Advantages of nuclear power, as a generative electricity source?

A

Nuclear fuels don’t produce carbon dioxide.

The fuel is readily available, meaning it reduces pressure of fossil fuel supplies.

Does not contribute to global warming.

Less nuclear fuel has to be used to produce the same amount of energy as a burning fossil fuel.

38
Q

Disadvantages of nuclear power, as a generative electricity source?

A

A lot of money and time is required to commission and decommission the stations- this may be bad for country’s economy.

Radioactive waste can be difficult to dispose of, and will remain radioactive for many years; thus is dangerous to environment and humans.

Workers have to be regularly checked as it is dangerous.

39
Q

Explain the process of fission of Uranium-235?

A

The U-235 absorbs a neutron; this makes it’s nuclei unstable, this causes it to split into two radioactive daughter nuclei and release two or more neutrons, as well as releasing energy,

40
Q

Why are reactions in a nuclear power station referred to as controlled chain reactions?

A

The neutrons released are absorbed by other nuclei, causing this nuclei to undergo fission again, releasing further neutrons. However, this is controlled by a control rod, which absorbs excess neutrons.

41
Q

What is the purpose of a moderator?

A

A moderator slows down the travelling neutrons until they are travelling slow enough for them to be absorbed. This increases the chance of a successful fission.

42
Q

How are control rods used to ensure a controlled reaction.

A

They are raised, and lowered to absorb more or less neutrons. The number of neutrons absorbed affects the amount of successful reactions that can take place.

43
Q

Explain how electricity is produced in a nuclear power station?

A

The reactions release thermal energy.
The energy is used to boil water and then produce steam.
This steam is then used to turn a turbine, which starts the generator.

44
Q

What is nuclear fusion?

A

The creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy.

45
Q

Where does fusion commonly occur?

A

In the sun - stars use fusion as their energy source.

46
Q

Why can’t nuclear fusion be used as the earths energy source?

A

On earth we can’t get high temperatures and pressures for nuclear fusion to happen, whilst still being cost-effective. This is needed because both nuclei are positive; high temperature is required to overcome the electrostatic repulsion between the two nuclei. Additionally high pressure is required to increase the chance of fusion between the nuclei.

47
Q

Why is fission used instead of fusion?

A

Fission can be used for nuclear power, and can be easily controlled, whereas fusion is hard to control. Fusion also requires very harsh conditions (high temperatures and pressures, whereas fission does not require that shiiiii.

48
Q

What do alpha particles consist of?

A

They contain 2 protons and 2 neutrons bound together into a particle, similar to a helium particle.

49
Q

What is a beta particle?

A

An electron emitted from a nucleus when a neutron becomes a proton.

50
Q

Why is radioactive waste a large issue?

A

Radioactive waste is a large issue, as since it stays radioactive for 10s of thousands of years, it can only be disposed of by burying it deep in landfill sites. It has to be placed in a glass box, then a metal container. If it were to leak ecosystems would be damaged.

51
Q

What is the role of shielding in a nuclear reactor?

A

It is usually made of 2m thick wall of steel, and surrounds the reactor. The purpose of this is to absorb any hazardous radiation that may leak to the enviroment.

52
Q

What are the control rods usually made of?

A

Control rods are made of boron.

53
Q

Describe the differences between fission and fusion?

A

Fusion is the process of joining together elements, while fission is the process of breaking apart elements.

Fusion occurs in stars, while fission occurs in nuclear reactors.

Fusion requires very high temperatures that aren’t economically possible on earth, while fission requires lower (possible temperatures.)

54
Q

What is the charge and mass of an alpha particle?

A

2+
4

55
Q

How to determine number of electrons in an atom?

A

Number of protons = Number of electrons

PHYSICS FLASHCARDS: (2 decks)

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