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The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to ( 1 / 16 ) th    of its initial value?

Option 1 -

80 minutes

Option 2 -

20 minutes

Option 3 -

40 minutes

Option 4 -

60 minutes

0 2 Views | Posted 2 months ago
Asked by Shiksha User

  • 1 Answer

  • A

    Answered by

    alok kumar singh | Contributor-Level 10

    2 months ago
    Correct Option - 2


    Detailed Solution:

    1 2 m u 3 2 - 1 2 m u 2 = - F R × 24

    0 - 1 2 m u 2 = - F R × d

    1 2 m u 2 1 2 m u 2 × 8 9 = d 24

    d = 24 × 9 8 = 27 c m

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