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Physics
Radioactive Decay and Half Life
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Created by
Abdullah Mahroof
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Cards (27)
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 emit radiation?
Radioactive
materials
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Why can't we predict when a single radioactive isotope will decay?
The decay
process
is completely random
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What can we determine from a large sample of radioactive isotopes?
The
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 taken for the number to
halve
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How can half-life be defined in terms of radioactive nuclei?
Time taken for nuclei to
halve
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How can half-life be defined in terms of activity?
Time taken for activity to
halve
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What happens to the number of unstable particles as time goes on?
The
number
of
unstable
particles
decreases
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Why does the overall rate of decay decrease over time?
Fewer
particles
are left to decay
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How is the decay process represented graphically?
Activity
plotted against time
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What does the curve of the decay graph indicate?
The
rate of decline
also falls
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How do you calculate half-life from a graph?
Find the time for
activity
to halve
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If the activity drops from 600 to 300, how long did it take?
About
two
hours
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If the activity drops from 300 to 150, how long does it take?
Another two
hours
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What does a shorter half-life indicate about a radioactive sample?
It
decays
more
quickly
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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
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If the half-life of a radioactive source is 40 hours, how many half-lives are in five days?
Three
half-lives
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How many radioactive nuclei remain after three half-lives from 3 million?
375,000
nuclei remain
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What are the key concepts of activity and half-life in radioactive decay?
Activity: overall rate of decay
Measured in
becquerels
Half-life: time for
quantity
to halve
Correlated with number of
radioactive nuclei
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How does the decay process of radioactive isotopes change over time?
Decay is random for individual isotopes
Overall
decay rate
decreases as
particles
decay
Activity declines and is represented by a curved graph
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How do you calculate the remaining radioactive nuclei after multiple half-lives?
Determine total time in hours
Divide by
half-life
to find half-lives
Halve the initial quantity for each half-life
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