Pick out the correct statements from the following:
$I$. Electron emission during $\beta$-decay is always accompanied by neutrino.
$II$. Nuclear force is charge independent.
$III$. Fusion is the chief source of stellar energy.

In a nuclear fusion process,the mass defect is $0.05\%$. How much energy will be released from $1 \, kg$ of mass?

In a reactor, $2 \, kg$ of ${ }_{92} U ^{235}$ fuel is fully used up in $30$ days. The energy released per fission is $200 \, MeV$. Given that the Avogadro number, $N_A = 6.023 \times 10^{26} \, \text{per kilo mole}$ and $1 \, eV = 1.6 \times 10^{-19} \, J$. The power output of the reactor is close to $..... \, MW$.

In a material medium,when a positron meets an electron,both particles annihilate,leading to the emission of two gamma-ray photons. This process forms the basis of an important diagnostic procedure called:

Consider the nuclear fission reaction ${ }_0^1 n+{ }_{92}^{235} U \longrightarrow{ }_{56}^{144} Ba+{ }_{36}^{89} Kr+3{ }_0^1 n$. Assuming all the kinetic energy is carried away by the fast neutrons only and total binding energies of ${ }_{92}^{235} U, { }_{56}^{144} Ba$ and ${ }_{36}^{89} Kr$ to be $1800 \ MeV, 1200 \ MeV$ and $780 \ MeV$ respectively,the average kinetic energy carried by each fast neutron is (in $MeV$):

Which of the following cannot cause fission in a heavy nucleus?