Multiple choice

The half-life of a radioactive substance is 30 minutes. During 2 hours, the fraction of the total number of atoms that have decayed would be ____________.

  1. 6.25%

  2. 12.5%

  3. 25%

  4. 87.5%

  5. 92.75%
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Half-life = 30 minutes For 2 hrs, the number of half-life (n) = 4 Cn = 1/2n= 1/24 = 1/16 = 6.25% So, after 2 hrs the amount of radioactive substance will be reduced to 1/16th (6.25%) of its initial amount. Hence, the amount decayed during 2 hrs = (100 - 6.25)% = 92.75%

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