Uses of Radiation- page 55

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  • Created by: emj790
  • Created on: 29-03-17 18:54
What do the hazards associated with a radioactive source depend on?
Its half life
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When is it safer to be around a radioactive source?
When it has a lower activity
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If two sources produce the same type of radiation and they have the same activity, which one is more dangerous?
The one with the longer half-life
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Why is this?
Because ,after any period of time, the activity of the source with a short half life will have fallen more than the activity with the long half-life
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What happens to the danger if two sources have different initial activity?
The danger associated with them changes over time.
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Which would be more dangerous?
The one with the longer half-life after a certain amount of time, otherwise the one with the higher activity
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Why?
Because its activity falls more slowly
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What is important choosing a radioactive source for an application?
To find a balance
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A balance between what?
A source that has the right levels of activity for the right amount of time, and that it isn't too dangerous for too long.
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What do you need to plan carefully?
A way to store and dispose the sources
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Especially for what?
Sources that have long half-lives
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Name a radiation use that uses Alpha
Smoke alarms / fire alarms
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What is placed in a smoke detector, close to what?
A weak source of alpha radiation close to two electrodes
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What does the source cause?
Ionisation
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What flows?
A current
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What happens if there is a fire?
The smoke will absorb the radiation
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What does this mean will happen?
The current will stop and the alarm will sound
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Name a use of gamma rays (not cancer related though)
The sterilisation of food and equipment
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What happens when food is irradiated with a high dose of gamma rays?
It will kill all microbes
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What does this mean about the food?
It won't go bad as quickly as it would do otherwise
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Medical equipment can be sterilised with gamma rays instead of what?
Instead of being boiled
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Why is irradiation a good method of sterilisation?
It doesn't involve high temperatures
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So what doesn't get damaged?
Fresh fruit or plastic instruments
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What does the radioactive source, used for this, need to be?
A very strong emitter of gamma rays with a reasonably long half-life
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What is a reasonable amount of time?
At least several months
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Why does it need to be this long?
So that it doesn't need replacing too often
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How else is radiation used?
In tracers and thickness gauges
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How is a medical tracer put into the patient?
It can be injected or swallowed
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How is it followed? (using what)
Using an external detector
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What can this method be used to do?
Detect and diagnose medical conditions (e.g. cancer)
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What do all isotopes taken into the body have to be?
Beta or gamma emitters
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Why?
So that the radiation passes out of the body without doing too much damage.
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How long should they last?
Only a few hours
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Why?
So that the radioactivity inside the patient quickly disappears
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Gamma emitting tracers are also used in what?
Industry to detect leaks in underground pipes
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What is used in thickness control? (type of radiation)
Beta radiation
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How does it work? What happens?
You direct radiation through the stuff being made (e.g. paper), and put a detector on the other side, connected to a control unit. When the amount of detected radiation changes, it means the paper is coming out too thick or thin.
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And what does the control unit do when this happens?
Adjusts the rollers to give the correct thickness.
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Why does it need to be a beta source?
Because then the paper will partly block the radiation. If it all goes through (or none of it does), then the reading won't change at all as the thickness changes.
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Explain why radioactive sources that emit alpha radiation are not used as medical tracers. [2 marks]
Alpha radiation is highly ionising so would damage cells in the body [1 mark]. Alpha radiation can't penetrate through tissue, so it wouldn't be detected outside the body with the radiation detector [1 mark].
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Other cards in this set

Card 2

Front

When is it safer to be around a radioactive source?

Back

When it has a lower activity

Card 3

Front

If two sources produce the same type of radiation and they have the same activity, which one is more dangerous?

Back

Preview of the front of card 3

Card 4

Front

Why is this?

Back

Preview of the front of card 4

Card 5

Front

What happens to the danger if two sources have different initial activity?

Back

Preview of the front of card 5
View more cards

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