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A radioactive sample has an initial acti...

A radioactive sample has an initial activity of 50 dpm, 20 minute later, the activity is 25 dpm . How many atoms of the radioactivity nuclide were there originally?

A

20

B

1000

C

1443

D

2

Text Solution

Verified by Experts

The correct Answer is:
C
Rate of decereses from 50 to 25 dpm in 20 min , hence half-life is 20 min .
Now, `r_(0) = lambdaN_(0) = (0.693)/(t^(1/2)) xx N_(0)`
or `N_(0) = (r_(0) xx t_(1/2))/(0.693) = (50 xx20)/(0.693) = 1443`
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