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Zorluk: KolayRadioactive Decay Law and Half-life

A radioactive sample has a half-life of 12 minutes12\text{ minutes}. If its initial activity is 96 Bq96\text{ Bq}, what is the remaining activity of the sample, in Bq\text{Bq}, after an elapsed time of 36 minutes36\text{ minutes}?

Cevap: 12 Bq

Cevap

The remaining activity of the radioactive sample after 36 minutes36\text{ minutes} is 12 Bq12\text{ Bq}.
In 36 minutes36\text{ minutes}, exactly 33 half-lives elapse (36/12=336 / 12 = 3). The remaining activity reduces to (1/2)3=1/8(1/2)^3 = 1/8 of the initial value, giving 96 Bq/8=12 Bq96\text{ Bq} / 8 = 12\text{ Bq}.

Adım Adım Çözüm

1
Calculate the number of half-lives that have elapsed
n=3n = 3
Divide the total elapsed time (36 minutes36\text{ minutes}) by the half-life duration (12 minutes12\text{ minutes}).
2
Calculate the remaining activity of the isotope
A=12 BqA = 12\text{ Bq}
After n=3n = 3 half-lives, the remaining activity fraction is (12)3=18\left(\frac{1}{2}\right)^3 = \frac{1}{8}. Multiplying initial activity 96 Bq96\text{ Bq} by 18\frac{1}{8} yields 12 Bq12\text{ Bq}.

Anahtar Kavram

Radioactive Decay Law and Half-life
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