Half-life 5 days. Fraction remaining after 15 days: MCQ with Answer and Explanation

Half-life 5 days. Fraction remaining after 15 days:
A. 1/3
B. 1/8
C. 1/2
D. 1/16
Answer: Option B
Solution (By JKSSB Mock Tests)
Number of half-lives n = 15/5 = 3. Fraction = (1/2)³ = 1/8. Exponential decay: N = N₀(1/2)^(t/T). Memory aid: 'After n half-lives: fraction = 1/2ⁿ'. Radioactivity calculation frequently tested in competitive exams with simple half-life arithmetic.

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