$\gamma$-rays radiation can be used to create an electron-positron pair. In this process of pair production,$\gamma$-rays energy cannot be less than ....... $MeV$.

Degenerate electron pressure will not be sufficient to prevent the core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is:

The curve of binding energy per nucleon as a function of atomic mass number has a sharp peak for the helium nucleus. This implies that helium

Nucleus $A$ has a mass number of $220$ and its binding energy per nucleon is $5.6 \, MeV$. It splits into two fragments '$B$' and '$C$' with mass numbers $105$ and $115$,respectively. The binding energy per nucleon for both '$B$' and '$C$' is $6.4 \, MeV$. The energy $Q$ released per fission will be............$MeV$.

${ }_{92}^{238} A \rightarrow{ }_{90}^{234} B +{ }_2^4 D + Q$
In the given nuclear reaction,the approximate amount of energy released will be $.....\,MeV$.
[Given: mass of ${ }_{92}^{238} A = 238.05079 \, u$,mass of ${ }_{90}^{234} B = 234.04363 \, u$,mass of ${ }_2^4 D = 4.00260 \, u$,and $1 \, u = 931.5 \, MeV/c^2$]

The binding energy per nucleon is maximum in the case of