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Question
CBSEENPH12039835

The half-life to a radioactive nucleus is 50 days. The time interval (t2-t1) between the time t2 when 2/3 of  it has decayed and the time t1 when 1/3 of it had decayed is

  • 30 days

  • 50 days

  • 60 days

  • 15 days

Solution

B.

50 days

Active space fraction space straight a space straight t space instant space straight t subscript 2
1 over 2 to the power of straight t subscript 2 divided by straight T subscript 1 divided by 2 end subscript end exponent space equals space 1 third
Active space fraction space straight a space straight t space instant space straight t subscript 1
1 over 2 to the power of straight t subscript 1 divided by straight T subscript 1 divided by 2 end subscript end exponent space equals space 2 over 3
2 to the power of straight t subscript 2 divided by straight T subscript 1 divided by 2 end subscript end exponent over 2 to the power of straight t subscript 1 divided by straight T subscript 1 divided by 2 end subscript end exponent space equals space 2

2 to the power of fraction numerator straight t subscript 2 divided by straight T subscript 1 divided by 2 end subscript over denominator straight t 1 divided by straight T subscript 1 divided by 2 end subscript end fraction end exponent space equals 2

straight t subscript 2 minus straight t subscript 1 space equals space straight T subscript 1 divided by 2 end subscript space equals space 50 space days

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