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Physics:
Radioactivity
half-life
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Half-life
The time it takes for the number of
nuclei
of a
radioactive
isotope in a sample to halve
Determining half-life
1. Measure the time it takes for the number of
undecayed
nuclei to
halve
2. Measure the time it takes for the
count rate
to
halve
Radioactive decay is a
random
process, so scientists cannot predict when a
nucleus
will decay
Radioactive isotopes with different half-lives
Isotope with relatively
long
half-life
Isotope with relatively
short
half-life
As the number of half-lives increases
The count rate
decreases
by
half
each time
Calculating
decrease
in count rate after a given number of half-lives
Divide
the
initial
count rate by
2
for each
half-life
that has passed
The
half-life
is the time it takes for the
count rate
or
activity
from a
sample
to fall to
half
its initial
level
The
count rate
is the number of decays per second recorded by a detector such as a
Geiger-Muller
tube
You can determine the half-life of an
isotope
from a graph showing the number of
undecayed nuclei
remaining over time
