In the disintegration series the $_{92}^{238}U\xrightarrow{\alpha }X\xrightarrow{{\beta - }}_Z^AY$ values of $Z$ and $A$ respectively will be
$92, 236$
$88, 230$
$90, 234$
$91, 234$
A nucleus $X$ undergoes following transformation
$X \stackrel{a}{\longrightarrow} Y$
$Y \underset{2 \beta}{\longrightarrow} Z$
then
If $_{92}{U^{238}}$ undergoes successively $8 \alpha$- decays and $6 \beta$- decays, then resulting nucleus is
The $\beta$-particles of a radioactive metal originate from
The total number of $\alpha$ and $\beta$ particles emitted in the nuclear reaction ${ }_{92}^{238} \mathrm{U} \rightarrow{ }_{82}^{214} \mathrm{~Pb}$ is
$\gamma$-rays radiation can be used to create electron-positron pair. In this process of pair production, $\gamma$-rays energy cannot be less than .......$MeV$