An electron and a positron annihilate each other to produce two $\gamma$-ray photons of equal energy. The minimum energy of each photon is .....

$A$ heavy nucleus having mass number $200$ gets disintegrated into two small fragments of mass numbers $80$ and $120$. If binding energy per nucleon for the parent atom is $6.5 \text{ MeV}$ and for the daughter nuclei is $7 \text{ MeV}$ and $8 \text{ MeV}$ respectively, then the energy released in the decay will be: (in $\text{ MeV}$)

The binding energy per nucleon versus mass number curve for nuclei is shown in the figure. $W, X, Y$ and $Z$ are four nuclei indicated on the curve. The process that would release energy is

$A$ nuclide $1$ is said to be the mirror isobar of nuclide $2$ if $Z_1 = N_2$ and $Z_2 = N_1$. $(a)$ What nuclide is a mirror isobar of $_{11}^{23}Na$? $(b)$ Which nuclide out of the two mirror isobars has greater binding energy and why?

For the decay of a nucleus,which of the following is $NOT$ a possible reason?

$M_p$ denotes the mass of a proton and $M_n$ that of a neutron. $A$ given nucleus,of binding energy $B$,contains $Z$ protons and $N$ neutrons. The mass $M(N, Z)$ of the nucleus is given by ($c$ is the velocity of light):