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Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What is radioactive decay?

A

Some isotopes have an unstable nucleus
To become stable, the nucleus gives out radiation
This process is radioactive decay

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2
Q

Can radioactive decay be predicted?

A

No, it is a completely random process and scientists cannot predict when it will occur

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3
Q

Activity

A

The rate at which a source of unstable nuclei decay

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4
Q

How do we measure activity and what’s the unit?

A

Using a Geiger-Muller tube
Becquerel (Bq)

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5
Q

What is the count rate in a Geiger-Muller tube?

A

Number of decays recorded each second by a detector
Ie the number of radioactive emissions picked up
But scientists can’t say for certain when this will happen

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6
Q

Alpha particles

A

A type of radiation
Consists of 2 neutrons and 2 protons
The same as a helium nucleus

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7
Q

Beta particles

A

A type of radiation
1 electron which is ejected from a nucleus at a very high speed when a neutron changes into a proton and electron

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8
Q

Gamma ray

A

Type of electromagnetic wave
Is radiation from the nucleus

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9
Q

Neutron radiation

A

Sometimes given off by an unstable nucleus, also a type of radiation

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10
Q

Properties of alpha particles

A

Large
Travels around 5cm in the air before stopping due to air particles
Stopped with a single sheet of paper
Strongly ionising - produces lots of ions when hitting an atom

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11
Q

Properties of beta particles

A

Travels around 15cm in the air
Stopped by a sheet of aluminium
Quite strongly ionising

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12
Q

Properties of gamma rays

A

Can travel several metres in the air before stopping
Has to be stopped by several cm of lead
Weak ionising

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13
Q

Ionising power

A

When radiation collides with atoms, that can cause atoms to lose electrons and form positive ions

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14
Q

Nuclear equations

A

Shows us what happens when a radioactive nucleus decays

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15
Q

Alpha decay equations

A

The atomic number decreases by 2
The mass number decreases by 4
Creates helium atom with a mass of 4 and number of 2

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16
Q

Beta decay equations

A

The atomic number increases by 1
The mass number does not change
Produced an electron with atomic number -1

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17
Q

Why does the atomic number in a beta decay increase by 1?

A

Because the neutron becomes a proton, increasing the atomic number

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18
Q

Risks of ionising radiation

A

Can penetrate skin cells, if it hits the DNA in the nucleus can cause a mutation and thus cancer

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19
Q

Uses of radiation in medicine as a tracer

A

Can be used as X-rays ro visualise damage to find tumours/ arthritis etc
To find problems in the thyroid gland which absorbs iodine. Drinking radioactive iodine then detecting the gamma rays that are emitted to see if too much/little has been absorbed

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20
Q

Count rate vs activity

A

Activity = rate at which unstable nuclei decay
Count rate = rate at which radioactive emissions are detected, effected by background radiation

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21
Q

What determines an isotope’s instability?

A

If it has too many or too few neutrons

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22
Q

Why is radioactive decay random?

A

A radioactive source has so many nucleus it’s impossible to predict when a particular one decays

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23
Q

Gamma decay equations

A

No change to atomic number or mass number

24
Q

Half life

A

Because a nuclei’s radioactive decay is random,
Scientists can’t state when individual nucleus decay
So we find time taken for half of the nuclei in a source to decay

25
Q

If nuclei have a short half life what does that show?

A

It is an unstable isotope
As it has to give out more radioactivity to achieve stability

26
Q

Half life in terms of count rate

A

Time it takes for count rate/ activity of the sample to fall to half of its initial rate

27
Q

How to find half life from a graph?

A

Find where half of the decays are on y axis
Draw lines from the y axis to the time using the graph at the x axis

28
Q

Irradiation

A

Exposing an object to nuclear radiation
Can be either alpha, beta, gamma, neutrons

29
Q

How can irradiation be used?

A

Sterilising medical equipment that can’t be heated normally

30
Q

How does sterilisation of medical equipment work?

A

Place equipment in plastic wrapper to stop bacteria entering
Place near a radioactive isotope, releasing gamma radiation
Use protection from lead shield then withdraw it to expose the equipment to gamma waves

31
Q

Ionising radiation risk

A

Can hit the atoms in our cells and form ions
Causing mutation in DNA and thus uncontrolled division = cancer

32
Q

How to be protected from alpha radiation?

A

Gloves

33
Q

How to be protected from beta or gamma radiation?

A

Lead apron

34
Q

If the levels of radiation are too high how else can we be protected?

A

Lead screen and lead glass
Use a radiation monitor to avoid contact with radioactive isotopes

35
Q

Radioactive contamination

A

When unwanted radioactive isotopes end up on materials
Causing the isotopes to decay and emit ionising radiation

36
Q

Why is alpha radiation dangerous when inside the body?

A

Crash into living cells
Damage DNA = mutation

37
Q

Is gamma radiation dangerous to humans?

A

Not too bad as it usually pases right through

38
Q

Peer review

A

Studies are published on affects of things eg radiation to be checked by other scientists

39
Q

Background radiation

A

Radiation around us all the time

40
Q

Sources of background radiation

A

Radioactive rock eg granite
Cosmic rays from space (high energy particles) due to supernovas
Nuclear weapon testing fall out
Accidents at power stations

41
Q

What affects exposure to background radiation?

A

Location eg places with a lot of granite
Occupation eg cabin crew with a lot of cosmic rays

42
Q

What is radiation dose measured in?

A

Sieverts (Sv)

43
Q

Radioactive isotopes as a medical tracer

A

Check how much iodine has been absorbed by the thyroid glands by swallowing radioactive iodine, decaying
Bone scans to visualise tumours off damage by arthritis

44
Q

What must a medical tracer be like?

A

Must pass out body (not alpha)
Not strongly ionising = damage
Not decay into another isotope
Short half life so not present for a long time

45
Q

Radiotherapy

A

Destroying cancer with ionising radiation

46
Q

How does radiotherapy work externally ?

A

External source of ionising radiation
Gamma rays pass into body and destroy tumour from

47
Q

Risks of external radiotherapy

A

Damages healthy tissue

48
Q

How does radiotherapy work internally?

A

Radioactive rods put inside the body

49
Q

Benefits of internal radiotherapy

A

Radiation precisely targets tumour
No damage to healthy tissue

50
Q

What are the stages of nuclear fission?

A

Unstable nucleus absorbs a neutron
Nucleus split to form smaller daughter nuclei, gamma, neutrons
The neutrons are absorbed by other unstable nucleus
Repeats

51
Q

Nuclear chain reaction

A

Nuclear fission
When unstable nucleus absorbs neutron which releases more neutrons to be absorbed by nucleus
Causing a large amount of energy to be released

52
Q

Controlled chain reaction

A

Scientists controlling nuclear fission to release energy in a nuclear reactor

53
Q

What causes a nuclear bomb?

A

Uncontrolled nuclear fission

54
Q

Nuclear fusion

A

2 light nuclei such as hydrogen join to create a heavier nucleus
This mass of the nuclei converted to energy, released as radiation

55
Q

What can nuclear fusion do?

A

Release energy in stars

Physics (44 decks)

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