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A radioactive sample has initial activit...

A radioactive sample has initial activity of 28 dpm 30 minutes later its activity 14 dpm . How many atoms of nuclide were present initially?

A

1200

B

400

C

600

D

800

Text Solution

Verified by Experts

The correct Answer is:
A
`t_(1//2)=(1)/(2)hr =30` min
`lambda=(0.693)/(t_(1//2))=(0.693)/(30) "min"^(-1)`
=0.0231
`(dN)/(dt)=lambda[N_(0)]`
`28=0.0231 [N]_(0)`
`[N]_(0)=(28)/(0.0231)=1212`
`~~1200` Ans.
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