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Half-Life - Measuring the Age of Archaeological Specimens (continued).
Archaeological specimens are things which belonged to people in the past
and have been dug up from the
ground.
Archaeological is pronounced
ar-key-o-logical.
Study
of these specimens can tell you
a lot about how people in the past
lived.
One of the most important things to
know is the age of the specimen
as this tells you how long ago the
thing was used (or living).
The half-life of carbon-14 is
5,730 years.
Question. If a specimen sample had an amount of carbon-14 which
was
25% of the amount in today's environment, how old would the sample
be?
Answer. Find how many half-lives
would be needed
to reduce the amount of carbon-14 to
25%.
After 2 half-lives the amount
of carbon-14 is reduced to
25%.
The sample is 2 x 5730 =
11,460 years old.
If the amount of carbon-14 was only
6·25%,
then the sample would be 4 half-lives
old.
4 half-lives are 4 x
5730 = 22,920
years old
(see uses and limitations).
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