Thermal neutrons are those which

$A$ nucleus with mass number $220$ initially at rest emits an $\alpha -$ particle. If the $Q$ value of the reaction is $7.8 \, MeV$ and subsequently after the emission of the $\alpha -$ particle,a photon of energy $1.2 \, MeV$ is also emitted. The kinetic energy of the $\alpha -$ particle is ? .......... $MeV$

$A$ nucleus is bombarded with a high-speed neutron so that the resulting nucleus is a radioactive one. This phenomenon is called:

The energy released in an atom bomb is obtained from?

$A$ $\gamma$-ray photon creates an electron-positron pair. If the rest mass energy of an electron is $0.51 \, MeV$ and the total kinetic energy of the electron-positron pair is $0.78 \, MeV$,then the energy of the $\gamma$-ray photon in $MeV$ is:

The physics behind a fusion test reactor is: