For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

1. 20

2. 30

3. 10

4. 15

Doubtly Asked 30 Oct 2026 NEET UG 2018 neet Save WhatsApp Report

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Answer: 1. 20

If 450 of 600 nuclei disintegrate, 150 remain, which is \(\dfrac14\) of the original.

\(\dfrac{N}{N_0}=\left(\dfrac12\right)^{n}=\dfrac14\Rightarrow n=2\) half-lives.

Time \(=2\times10=20\) minutes.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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