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physics
physics paper 1
half lifes
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Created by
Grace Abodunwa
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Cards (23)
What are the two terms discussed in the video?
Activity
and
half-life
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What happens to unstable isotopes to become more stable?
They
decay
by emitting
radiation
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What do we call materials that contain unstable isotopes?
Radioactive
materials
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Why can't we predict when a single radioactive isotope will decay?
Because the
decay
process
is
random
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What can we determine from a large sample of radioactive isotopes?
Activity and
half-life
of the sample
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How is activity measured?
In
becquerels
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What does one becquerel represent?
One
decay
per
second
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If a sample has an activity of 600 becquerels, how many isotopes decay each second?
600 isotopes
decay each second
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What is half-life defined as?
The time for
radioactive
nuclei to halve
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How can half-life be defined in terms of activity?
As the time taken for activity to
halve
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If a sample starts with 1 million unstable nuclei, how many will remain after one half-life?
500,000
unstable nuclei
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How does the decay process affect the overall rate of decay?
It decreases as fewer
particles
remain
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What does a graph of activity against time show?
Decline in
particles
and activity over time
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How do you calculate half-life from a graph?
Find time for
activity
to halve
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What is the half-life of the sample in the example given?
Two
hours
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What device is used to find the activity of a radioactive sample?
Geiger-Muller
tube
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What does a Geiger-Muller tube record?
Decays that reach it each
second
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What is the count rate used for?
To estimate the
activity
of a sample
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If the half-life of a radioactive source is 40 hours, how many half-lives are in 5 days?
Three
half-lives
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How many radioactive nuclei remain after three half-lives from 3 million?
375,000
radioactive nuclei
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What are the key concepts of radioactive decay discussed in the video?
Activity
: overall rate of decay
Half-life
: time for
nuclei
or activity to
halve
Random decay process
Decrease in activity over time
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How do the concepts of activity and half-life relate to each other?
Fewer
radioactive
nuclei lead to lower activity
Both concepts are correlated
Activity decreases as half-life progresses
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How do you determine the remaining radioactive nuclei after multiple half-lives?
Calculate total time in hours
Divide by
half-life
to find half-lives
Halve the initial amount for each half-life
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