A sample of radioactive element containing $4 \times 10^{16}$ active nuclei. Half life of element is $10$ days, then number of decayed nuclei after $30$ days is ........ $\times 10^{16}$
$0.5$
$2$
$3.5$
$1$
A nucleus has a half-life of $30\; min$. At $3 \;PM$ its decay rate was measured as $120000 \,cps$. the decay rate ........... $\,cps$ at $5 \,PM$ ?
Which of the following Statements is correct?
The half life period of a radioactive substance is $5\, min$. The amount of substance decayed in $20\, min$ will be..........$\%$
$N$ atoms of a radioactive element emit $n$ number of $\alpha$-particles per second. Mean life of the element in seconds, is
Given below are two statements :
Statement $I:$ The law of radioactive decay states that the number of nuclei undergoing the decay per unit time is inversely proportional to the total number of nuclei in the sample.
Statement $II:$ The half life of a radionuclide is the sum of the life time of all nuclei, divided by the initial concentration of the nuclei at time $t =0$.
In the light of the above statements, choose the most appropriate answer from the options given below :