Question

One gram of a radioactive material having a half-life period of 2 years is kept in store for a duration of 4 years. Calculate how much of the material remains unchanged

Answer 1

Using law of radio activity, $N=N_0{e}^{-\lambda t}$

Here decay constant, $\lambda =0.693/t_{1/2}=0.693/2=0.35yea{r}^{-1}$

Thus, $N=1e^{-0.35\times 4}=0.25gram$