Cesium 137 is a radioactive metal with a short half-life of 30 years. In a
sample originally having 1 gram of cesium 137, the amount of cesium 137 present after t years is given by
A(t) = (1/2)^t/30. where A is the amount of cesium in grams and t is the time in years.
a. How much cesium 137 will be present after 30 years?
b. How much cesium 137 will be present after 90 years?
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(a) 30 years is one half-life.
THEREFORE, the remaining mass of the 1 gram of cesium-137 after 30 years is = 0.5 grams.
You will get the same answer, if you substitute the value t= 30 years into the given exponential decay function.
(b) 90 years is 3 (three) half-lives.
THEREFORE, the remaining mass of the 1 gram of cesium-137 after 90 years is = = = 0.125 grams.
You will get the same answer, if you substitute the value t= 90 years into the given exponential decay function.
Solved.
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