The half-life period of radium is $1600$ years. Its average life time will be ....... years.

The activity of a radioactive sample reduces from $A_0$ to $\frac{A_0}{\sqrt{3}}$ in $1$ hour. What will be the activity after $3$ hours more?

The activity of a radioactive sample is $6000 \, dps$ after $280$ days. After another $140$ days,the activity decreases to $3000 \, dps$. The initial activity of the radioactive sample (in $dps$) is ........

Three-fourths of the active nuclei decay in a radioactive sample in $3/4 \, s$. The half-life of the sample is:

$A$ radioactive element will decay by $99\%$ between which of the following number of half-lives?

The half-life period of a radioactive substance is $60 \ days$. The time taken for $\frac{7}{8}$ of its original mass to disintegrate will be $...... \ days$.