1.

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 isA. (a) 6000B. (b) 9000C. (c) 3000D. (d) 24000

Answer» Correct Answer - D
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 remain 1/4th of the initial activity.
Hence, the initial activity of the sample is `4xx6000 dps=24000dps`
Therefore, the correct option is (d).


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