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MHT CET 2025 (5 May, Shift 2) · Law of Radioactive Decay

Law of Radioactive Decay question from MHT CET 2025 (5 May, Shift 2)

Q14MHT CET 2025 · 5 MAY · SHIFT 2Easy

Law of Radioactive Decay

A radioactive element having half-life 30 min. is undergoing beta decay. The fraction of radioactive element remains undecayed after 90 min. will be

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Answer: (c)

Number of half-lives $n = \frac{90}{30} = 3$ .
Undecayed fraction $= \left(\frac{1}{2}\right)^3 = \frac{1}{8}$ (type of decay does not matter).
So the answer is (c) $\frac{1}{8}$ .

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