# Topic 4-Half-Life

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• Created by: claire
• Created on: 08-06-17 20:36
How can radiation be measured?
With a Geiger-Muller tube and counter (Geiger counter). It records the count-rate which is the number of counts reaching it per second.
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What is half-life?
It is the time it takes for the number of radioactive nuclei in an isotope to halve. Radioactive decay is completely random but it can be used to make predictions about radioactive sources.
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What can half-life be used to find?
The rate at which a source decays-it's ACTIVITY which is measured in becquerels, Bq (where 1 Bq is 1 decay per second).
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What is the problem with trying to measure the radioactivity of a source?
The activity never reaches zero.
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What does the radioactivity of a source do over time?
It decreases-each time a radioactive nicleus decays to become a stable nucleus, the activity will decrease. It can take a couple of hours to millions of years.
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What does a short half-life mean?
The activity falls quickly as the nuclei are very unstable and decay rapidly. These are dangerous because they emit a lot of radiation at the start of the process but they become safe very quickly.
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What does a long half-life mean?
The activity falls slower than a short half-life as most of the nuclei are quite stable and don't decay for a long time, the source just emits very small amounts for up to millions of years. It is dangerous as people can be exposed for a long time.
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## Other cards in this set

### Card 2

#### Front

What is half-life?

#### Back

It is the time it takes for the number of radioactive nuclei in an isotope to halve. Radioactive decay is completely random but it can be used to make predictions about radioactive sources.

### Card 3

#### Front

What can half-life be used to find?

### Card 4

#### Front

What is the problem with trying to measure the radioactivity of a source?

### Card 5

#### Front

What does the radioactivity of a source do over time?

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