Decay of a radioactive sample is `4.9xx10^(-18)s^(-1)`. Choose the correct statements regarding this sample.

Options

A. Average life is `6.49xx10^(9)` years
B. Half life is `4.5xx10^(9)` years
C. Activity of the sample decreases by 4 in `9xx10^(9)` years
D. `87.5%` of the initial number of nuclei is decayed in time `13.5xx10^(9)` years

Answer

A, B, C, D

Explanation

`lamda =4.9xx10^(18)s^(-1)`
`tau_("avg")=1/(lamda)=6.49xx10^(9)` years
`t_(1//2)=0.693/(lamda)=4.5xx10^(9)` years
NO of nuclei's remaining after `9xx10^(9)` hrs is `(N_(0))/4`
`implies` activity reduces to `1/4`
After 3 half lives neclei decayed is `87.5%`