Half-Life

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What do radioactive substances give out from their nuclei no matter what?
They give out radiation no matter what, it is a random process
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What can radiation be measured with?
A Geiger-Muller tube and counter
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what does a A Geiger-Muller tube and counter do?
Records the count rate - the number of radiation counts reaching it per second
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Why cant you predict exactly which nucleus in a sample will decay
Because radioactive decay is entirely random
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What is half-life?
The time it takes for the amount of radiation emitted by a source to halve
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What can half life be used for?
To make predictions about radioactive sources, even though their decays are random
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What can half-life also be used for?
to find the rate at which a source decays - its ACTIVITY
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What is activity?
activity is the rate at which a source decays
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What is activity measured in?
Becquerels, Bq (where 1 Bq is 1 decay per second)
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What happens each time a radioactive nucleus decays to become a stable nucleus
The activity as a whole will decrease (older sources emit less radiation)
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How long does it take for all the unstable nuclei in isotopes to decay?
Its takes just a few hours to millions of years?
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What problem is there with trying to measure activity?
The activity never reaches zero
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Why do we use the idea of half life to measure how quickly the acitivity drops off
Because the activit never reaches zero.
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What is half life?
Half life is the time taken for the number of radioactive nuclei in an isotope to halve
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Half life is also...?
The time taken for activity, and so count rate to halve
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What does short half life mean?
It means the actitivity falls quickly because the nuclei are very unstable and rapidly decay
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Why are sources with a short half life dangerous?
because of the high amount of radiation they emit at the start, but they quickly become safe
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What does a long half life mean?
It means the activity falls more slowly because most of the nuclei dont decay for a long time
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Why are sources with a long half life dangerous?
because the source just sits there, releasing small amounts of radiation for a long time meaning nearby areas are exposed to radiation for millions of years
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Other cards in this set

Card 2

Front

What can radiation be measured with?

Back

A Geiger-Muller tube and counter

Card 3

Front

what does a A Geiger-Muller tube and counter do?

Back

Preview of the front of card 3

Card 4

Front

Why cant you predict exactly which nucleus in a sample will decay

Back

Preview of the front of card 4

Card 5

Front

What is half-life?

Back

Preview of the front of card 5
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