Suppose the half-life of an isotope is 10 years. after how many years will half of this isotope have decayed into its daughter element?

5 years
10 years
20 years

A "half-life" is the amount it takes for a substance to decay toone-halff of the original amount. For example, if i have 100 gram of a substance that has a half-life of 5 min, 5 min later i'll have 50 grams. In this case, it will take 10 years to decay the isotope to half its original value.

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