The activity of a radioactive material is $2.56 \times 10^{-3} \,Ci$. If the half life of the material is $5$ days, after how many days the activity will become $2 \times 10^{-5} \,Ci$ ?

The decay constants of a radioactive substance for $\alpha $ and $\beta $ emission are ${\lambda _\alpha }$ and ${\lambda _\beta }$ respectively. If the substance emits $\alpha $ and $\beta $ simultaneously, then the average half life of the material will be

Calculate the time (in $minutes$) interval between $33 \,\%$ decay and $67\, \%$ decay if half-life of a substance is $20\, minutes.$

The decay constant of a radio active substance is $0.173\, (years)^{-1}.$ Therefore :

The half-life of a radioactive nuclide is $100 \,hours.$ The fraction of original activity that will remain after $150\, hours$ would be :

A certain radioactive material can undergo three different types of decay, each with a different decay constant $\lambda_1$, $\lambda_2$ and $\lambda_3$ . Then the effective decay constant is