What are the applications of radioactivity

${}_{12}{}^{27}\mathrm{Mg}\stackrel{\mathrm{\beta }}{\to }\mathrm{Al}\stackrel{\mathrm{\gamma }}{\to }$

In the above nuclear reaction.

Aluminium emits $\gamma$-ray. What is the resulting nucleus?

What are beta rays and gamma rays?

Name the natural radiations due to cosmic rays from the outer space.

Explain briefly what change takes place within the nuclei when beta particles are emitted by a radioactive substance.

In the nuclear decay given below :

${}_Z{}^A\mathrm{X}\to {}_{Z+1}{}^A\mathrm{Y}\to {}_{Z-1}{}^{A-4}\mathrm{B}^{*}\to {}_{Z-1}{}^{A-4}\mathrm{B}$ 

The particles emitted in the sequence are: