In a radioactive reaction $_{92}{X^{232}}{ \to _{82}}{Y^{204}}$, the number of $\alpha - $ particles emitted is

The mean life of a radioactive material for alpha decay and beta decay are, respectively, $1620$ years and $520$ years. What is the half life of the sample (in years) ?

The half life of the isotope $_{11}N{a^{24}}$ is $15 \,hrs$. How much time does it take for $\frac{7}{8}th$ of a sample of this isotope to decay.........$hrs$

Draw a graph showing the variation of decay rate with number of active nuclei. 

The half life of a radioactive substance against $\alpha  - $ decay is $1.2 \times 10^7\, s$. What is the decay rate for $4.0 \times 10^{15}$ atoms of the substance

At a given instant, say $t = 0,$ two radioactive substances $A$ and $B$ have equal activates. The ratio $\frac{{{R_B}}}{{{R_A}}}$ of their activities. The ratio $\frac{{{R_B}}}{{{R_A}}}$ of their activates after time $t$ itself decays with time $t$ as $e^{-3t}.$ If the half-life of $A$ is $ln2,$ the half-life of $B$ is