The half-life period for a radioactive substance is $15$ minutes. How many grams of this radioactive substance is decayed from $50$ g of substance after $1$ hour?

To determine the half-life of a radioactive element,a student plots a graph of $\ln|dN(t)/dt|$ versus $t$. Here $dN(t)/dt$ is the rate of radioactive decay at time $t$. If the number of radioactive nuclei of this element decreases by a factor of $p$ after $4.16 \ \text{years}$,the value of $p$ is

If a substance with a half-life of $3 \ days$ is kept for $12 \ days$,what fraction of the substance remains?

$A$ freshly prepared radioactive source of half-life $2 \ hours$ emits radiations of intensity which is $64$ times the permissible safe level. The minimum time after which it would be possible to work safely with this source is ......... $hours$.

$_{11}Na^{24}$ has a half-life of $15 \ h$. On heating,its half-life will:

What is the percentage of a radioactive element decayed after $20 \ s$ if its half-life is $4 \ s$?