Modern Physics Ques 108
- 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
(2004, 2M)
(a) $6000$
(b) $9000$
(c) $3000$
(d) $24000$
Show Answer
Answer:
Correct Answer: 108.(d)
Solution:
Formula:
- 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 $\frac{1}{4}$ th of the initial activity.
Hence, the initial activity of the sample is
$ 4 \times 6000 $ dps=$24000$ dps
BETA
