A radioactive sample has a half-life of 5 years. What fraction of the original active nuclei will remain undecayed after 15 years? MCQ with Answer and Explanation

A radioactive sample has a half-life of 5 years. What fraction of the original active nuclei will remain undecayed after 15 years?
A. 1/3
B. 1/15
C. 1/8
D. 1/2
Answer: Option C
Solution (By JKExamLibrary)
The number of half-lives (n) that have passed is total time / half-life = 15 / 5 = 3 half-lives. The fraction of the sample remaining undecayed is given strictly by the formula (1/2)^n. Therefore, the fraction remaining is (1/2)^3 = 1/2 * 1/2 * 1/2 = 1/8.

This question belongs to: Science Physics

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This question belongs to: Science Physics