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Physics · PYQ NEET UG 2016(2)
हिन्दीThe half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is
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Correct answer · Option A
60
Explanation
At 40% decay, remaining is 60% \( (N_1 = 0.60 N_0) \). At 85% decay, remaining is 15% \( (N_2 = 0.15 N_0) \). Since \( N_2 = N_1 / 4 \), the time elapsed is two half-lives, i.e., \( 2 \times 30 = 60 \) minutes.
