Question

It is observed that only 6.25% of a given radioactive sample is left undecayed after a period of 16 days. What is the decay constant of this sample in `day^-1`?

Answer 1

Here, `N/(N_0)=6.25/100=0.25/4`,
`t=16days. lambda=?`
As `N/(N_0)=(1/2)^n=0.25/4=1/16=(1/2)^4`
`:. n=4` As `n=t/T=,T=t/n=16/4=4 days`
Decay constant `lambda=0.693/T=0.693/4`
`=0.173day^-1`