Heavy water is used as a moderator in a nuclear reactor because

In any fission process,the ratio $\frac{\text{mass of fission products}}{\text{mass of parent nucleus}}$ is

The solar energy is primarily due to:

In the given nuclear reaction
${ }_{4}^{9} Be+{ }_{2}^{4} He \rightarrow{ }_{6}^{12} C+X$
$X$ represents $\qquad$

If $200 \, MeV$ energy is released in the fission of a single ${U^{235}}$ nucleus, the number of fissions required per second to produce $1 \, kW$ power shall be (Given $1 \, eV = 1.6 \times 10^{-19} \, J$)

In an $\alpha -$ decay,the kinetic energy of the $\alpha -$ particle is $48 \ MeV$ and the $Q$ value of the reaction is $50 \ MeV$. The mass number of the mother nucleus is (assume that the daughter nucleus is in the ground state).