I'm Late, I'm Late, for a Radioactive Date! Student Sheet #3 Name: ______________________________________ Amount of Pu in grams # of half-lives (time periods) Time in Years Fraction of Pu left Percent of Pu left 100 g 0 0 (start) 1 100%   1 5 years 1/2 50%   2 10 years 1/4     3 15 years       4         5         6       What is the general formula for determining half-life? _________________ Interactive Site: http://vcourseware.sonoma.edu/VirtualDating/files/RC0/RC_0.html Answer the following: 1. Generated in the upper atmosphere, C-14 makes up only ____% of all carbon atoms. 2. Because of interaction and exchange with atmosphere and oceans, all living tissue maintains a _______ proportion of C-14. After death, the amount of C-14 begins to ______________. 3. A C-14 date estimates the time since the death of once-living things, up to about _________years. 4. What percent of original C-14 can be found in a sample after 10 HL? ____ 5. Why is the daughter product, N-14, not retained by a specimen?  _______  __________________________________________________________ 6. Use the decay calculator to determine the age of a rock that has 87% of its mass. __________BP. 7. Use the calculations for the above in BP, substitute it into the calculator, and determine the date in A.D. _________A.D. 8. Explain why the amount of C-14 produced in the Earth's upper atmosphere from cosmic rays striking N-14 is or is not constant over time. __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ 9. What would be the age if you used the calibration or correction curves for the time in question 6? _______________A.D.