The average life $T$ and the decay constant $\lambda$ of a radioactive nucleus are related as

Radon $({Rn})$ decays into Polonium $({Po})$ by emitting an $\alpha$-particle with a half-life of $4\, days$. $A$ sample contains $6.4 \times 10^{10}$ atoms of $Rn$. After $12\, days$,the number of atoms of $Rn$ left in the sample will be:

If a radioactive material remains $25 \%$ after $16$ days,then its half-life will be ......... days.

The radioactivity of a sample is $R_1$ at a time $T_1$ and $R_2$ at a time $T_2$. If the half-life of the specimen is $T$,then the number of atoms that have disintegrated in the time interval $(T_2 - T_1)$ is proportional to

The half-life of a radioactive substance is $18 \text{ minutes}$. The time interval between its $20 \%$ decay and $80 \%$ decay in minutes is

The half-life period of a radioactive sample is $3.8 \ days$. After how many days will the sample become $\frac{1}{8}$ of the original substance?