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A radioactive element disintegrates for ...

A radioactive element disintegrates for a time interval equal to its mean life. The fraction that has disintegrated is

A

`1/e`

B

`1-1/e`

C

`0.693/e`

D

`0.693(1-1/e)`

Text Solution

Verified by Experts

The correct Answer is:
B
Number of atoms disintegrated,
`N=N_0(1-e^(-lambdat))`
`:.` `N/N_0=1-e^(-lambdat)`
At `t=`one mean life `=1/lambda`
`N/N_0=1-e^-1=1-1/e`
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