A sample of a radioactive element has a mass of `10 g` at an instant `t=0`. The approxiamte mass of this element in the sample after two mean lives is .

Options

A. `1.35 g`
B. `2.50 g`
C. `3.70 g`
D. `6.30 g`

Answer

a

Explanation

Let `t=0, M_(0) =10g`
`t=2 tau 2((1)/(lambda))`
Then,
`M=M_(0) e^(- lambdat) =10e^(-lambda)((2)/(lambda)) =10((1)/(e))^(2)1.35g `.