Outside a nucleus,which of the following statements is true?

$A$ nuclear reaction is given by ${}_{Z}X^{A} \to {}_{Z+1}Y^{A} + {}_{-1}e^{0} + \bar{\nu}$,which represents:

$A$ radioactive nucleus of mass $M$ emits a photon of frequency $v$ and the nucleus recoils. The recoil energy will be

Two radioactive substances $A$ and $B$ of mass numbers $200$ and $212$ respectively, show spontaneous $\alpha$-decay with the same $Q$ value of $1 \text{ MeV}$. The ratio of energies of $\alpha$-rays produced by $A$ and $B$ is . . . . . . .

Which of the following is in the increasing order for penetrating power?

$A$ positron is emitted from ${}^{23}Na_{11}$. The ratio of the atomic mass and atomic number of the resulting nuclide is