Half-Life - A Useful Concept
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On the animated graph below, click and move the slider to the right to simulate the passage of time in a mineral. Each decay of a radioactive parent isotope leaves behind a stable daughter isotope. Notice the decrease in parent U-235 (red spots) and the simultaneous increase in daughter Pb-207 (blue spots) as time passes. The red and blue curves represent the changing amounts of parent and daughter isotopes, respectively.
Each division on the slider represents one half-life, which is the amount of time required for one-half of a given amount of parent isotopes to decay. The half-life for U-235 is 713 million years. Other parent isotopes have shorter or longer half-lives.
Answer these questions, then click the "Next" Button.
Approximately what percentage of parent isotopes remains after 2 half-lives have passed?
If a rock initially contained 10 milligrams of a radioactive parent when it first crystallized, how much remains after 4 half-lives?
What % parent remains after 10 half-lives?
If a mineral contains1.56% of its original parent isotopes, how many half-lives have passed?