Physics - Modern Physics Question with Solution | TestHub

$\frac{N}{N_0}=e^{-\lambda t}$

$\frac{10}{100}=e^{-\lambda 5}$

$\frac{N}{N_0}=e^{-\lambda 20}$

$\frac{ln\frac{10}{100}}{ln\frac{N}{N_0}}=\frac{5}{20}$

$\frac{N}{N_0}=0.656$

$\therefore$The fraction of material decayed is

$=1-0.656=0.344$

$=34.4\%$