The C-14 Decay Curve
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After the death of an organism, C-14 decays to N-14. The rate, as for all radioactive decay, is related to the amount of C-14 present at any given time. In principle, any material that still has a sufficient amount of C-14 can be dated, with the date representing the time since the material stopped exchanging carbon with the atmosphere.

The illustration below demonstrates how the amount of radioactive C-14 decreases with time. Use the numerical spinner below the illustration to change the illustrations through time. Each number is one half-life different in time than the preceding or following one. The daughter product, N-14, is not retained by a specimen because it is a gas and escapes as it forms.

Answer these questions and then click the next button to continue.


What % of C-14 remains in a carbon-bearing material after 3 half-lives of time have gone by?
  50% 25 % 12.5% 6.25% 0.39%
2. How many half-lives of time have passed when only a little more than 3% of a sample original C-14 still remains?
  1 3 5 7 unknown
3. How much daughter N-14 can be found in a buried ancient tree stump that is 4 half-lives old?
  6.25% 93.75% 4% 96% Very little since N-14 is a gas and escapes from the material
4. What fraction of original C-14 can be found in a sample after 10 HL?
  over 1/10 between 1/10 and 1/100 between 1/100 and 1/1000 less than 1/1000 none

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