A radioactive substance has 0.1 gm at a particular instant and has an average life of 1 day . The mass of the substance which decays during the 4th day is give by :

Options

A. `6.25 mg`
B. `12. 5 mg`
C. `3.2 mg`
D. `1.25 mg`

Answer

C

Explanation

`[t=(1)/(lambda)=1]`day
After 3 days left
`w_(1)=wxx e^(-lambdat)`
`w_(1)=wxx e^(-3)`
After 4 days left
`w_(2) =w xx e^(-4)`
`w_(1)-w_(2) =we^(-3)=0.1 [ (1)/(e^(3))-(1)/(e^(4))]=3.2 mg `