A radioactive substance has a half life of 20 days. What ...
A radioactive substance has a half life of 20 days. What fraction of the original radioactive nuclei will remain after 80 days?
132
116
18
14
Correct answer is B
80 days = 4 half lives (i.e 4 x 20dqs = 80dq)
But the fraction always left by any radioactive material after 4 half lives is
(12)4=116
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