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  • After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is:<div class='qna-op

After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another
140 days. The initial activity of the sample in dps is:

Option: 1

6000


Option: 2

9000


Option: 3

3000


Option: 4

24000


Answers (1)

Activity reduces from 6000 dps to 3000 dps in 140 days. It implies that half life of the radioactive sample is 140
days.

In 280 days (or two half lives), activity will become \left(\frac{1}{4}\right)^{\text {th }} of the initial activity. As the activity left is 6000 \, \mathrm{dps}, therefore, initial activity of the sample =4 \times 6000=24000 \, \, \mathrm{dps}.

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Kshitij

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