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physics (paper one) > hazards and uses of radioactivity (topic 4) > Flashcards

hazards and uses of radioactivity (topic 4) Flashcards

1
Q
A
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2
Q
A
  • y
  • least ionising
  • penetrates through the body
  • is a gas so can be breathed in
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3
Q
A
  • longer shelf life
  • food can be supplied from around the world
  • less likely to get food poisoning
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3
Q
A

alpha - stopped by paper
beta - travels 1 metre
gamma - travels at speed of light

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4
Q
A
  • higher in village B
  • by 6 units
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5
Q

describe the structure of the three main types of ionising radiation (3)

A
  • alpha - helium nuclei (or 2 protons and 2 neutrons)
  • beta - high speed electron
  • gamma - high energy electromagnetic wave
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6
Q

explain the precautions that must be taken when handling radioactive materials (2)

A
  • limit the time of exposure
  • maintain a safe distance from the source
  • use shielding materials such as lead
  • handle with tongs
  • suitable protective clothing
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7
Q

describe how radioactive tracers are used in medical imaging (2)

A
  • radioactive tracer is injected OR radioactive tracer is ingested
  • radiation emitted by the tracer is detected, creating an image of the area being examined
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8
Q

a patient is given a dose of technetium-99m with an initial activity of 296 MBq, calculate the activity of the tracer after 18 hours

A
  • 18 hours = 3 half lives
  • initial activity = 296 MBq
  • after 1 half life - 6 hours = 148 MBq
  • after 2 half lives - 12 hours = 74 MBq
  • after 3 half lives - 18 hours = 37 MBq
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9
Q

describe how radioactive substances are used in radiotherapy for cancer treatment (2)

A
  • radioactive sources emit ionising radiation
  • that damages cancerous cells (or kill cancer cells)
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10
Q

describe how radioactive substances are used in smoke detectors

A
  • alpha particles ionise the air
  • creating a current
  • this current is interrupted when smoke enters the detector
  • triggering the alarm
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11
Q

describe the potential safety concerns related to the use of alpha radiation in smoke detectors (2)

A
  • alpha particles are highly ionising
  • harmful if ingested or inhaled
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12
Q

describe the precautions and safety measures taken to minimise the risks associated with using alpha-emitting sources in smoke detectors (2)

A
  • alpha has a low penetrating capability so wont be able to get outside the smoke detector
  • alpha has a very low range in air
  • alpha source is enclosed, preventing direct exposure to alpha radiation
  • the amount of radioactive material used in smoke detectors is very small
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13
Q

describe the relationship between the counts detected and the thickness of the aluminium sheets (2)

A
  • as the thickness increases, the counts detected decrease
  • in a non-linear way
  • thickness is inversely proportional to the counts detected
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14
Q

explain how beta radiation is used to measure the thickness of materials in this application (3)

A
  • radioactive source that emits beta particles is placed on one side of the material
  • geiger-Muller tube is placed on the opposite side of the material
  • as the thickness varies, the number of beta particles that are detected varies
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15
Q

explain how radioactive tracers are used to detect leaks in pipelines (3)

A
  • radioactive material is placed into the pipeline fluid
  • detectors placed along the pipeline to monitor the radiation levels outside the pipe
  • an increase in radiation levels detected indicates position of a leak
16
Q

Describe the advantages and safety precautions of using radioactive tracers for leak detection in pipelines.

A

advantages:
- ability to detect leaks in inaccessible or underground pipes
- high sensitivity for leak detection
safety precautions (max 2 marks):
- must use a radioactive isotope with a suitable-half life to prevent unnecessary long term radiation levels
- radioactive sources must be stored in suitable containers such as lead lined boxes
- radioactive sources must be handled with care

17
Q

explain what is meant by background radiation and give one source of background radiation (2)

A
  • low level radiation that is present in the environment at all times
  • cosmic rays
  • natural radioactive materials in the earth
  • human-made sources like medical tracers
  • some foods
18
Q

a student places an alpha source near a Geiger-Muller tube and records a count of 185 in 30 s, calculate the corrected count rate (in counts per minute)

A
19
Q

radium-223 can be put inside the body to treat cancers, radium has a half-life of 11.4 days and emits alpha radiation, explain why radium-223 is suitable for use inside the body to treat cancers

A
  • alpha is highly ionising
  • alpha kills cancer cells
  • alpha does not penetrate very far in the body
  • half-life is long enough for the treatment to take effect
  • half-life is short enough that the radiation does not need to be removed (or half-life is short enough that it won’t last very long in the body)
20
Q
A

9 MBq

21
Q
A

beta

22
Q

explain what is meant by a half-life of 6 hours (1)

A

activity of the sample will half every 6 hours (or number of radioactive parent nuclei halves every 6 hours)

23
Q

the radiographer wants the activity of the tracer to be less than 1 MBq after one day, calculate the maximum initial activity of the tracer if it is to have an activity of less than 1 MBq after one day

A
  • number of half lives = 24 ÷ 6 = 4
  • activity after 4 half lives = 1 MBq
  • activity after 3 half lives = 2 MBq
  • activity after 2 half lives = 4 MBq
  • activity after 1 half life = 8 MBq
  • initial activity = 16 MBq
24
Q

explain why alpha emitters are not used as tracers for medical imaging (3)

A
  • alpha is highly ionising
  • alpha can kill healthy cells
  • alpha would not be detected outside the body as it has a low penetrating ability
25
Q

(3)

A
  • alpha radiation is not suitable as it is absorbed by the plastic
  • beta radiation is suitable as it shows a clear and gradual decrease in counts detected as the thickness increases
  • gamma radiation is less suitable than beta, as it shows a smaller change in counts detected
  • gamma is less sensitive to variation in thickness
26
Q

describe how the workers at the factory could correct their recorded value to account for background radiation (factory uses radiation to monitor the thickness of plastic sheets) (3)

A
  • record the count for a set period of time with no source present
  • record the count with sources present for the same period of time
  • corrected count = count - background count
27
Q

the factory records the background radiation to be 1 count per second, the factory wants to maintain a plastic sheet thickness of 1.5 mm, calculate the corrected count for beta radiation to ensure the desired thickness is maintained

A
  • background count in one minute = 1 x 60 = 60 cpm
  • corrected count = 170 - 60 = 110 cpm

physics (paper one) (25 decks)

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