If an electron and a positron annihilate, then the energy released is:

1. $3.2\times {10}^{-13}$ $\mathrm{J}$       

2. $1.6\times {10}^{-13}$ $\mathrm{J}$

3. $4.8\times {10}^{-13}$ $\mathrm{J}$           

4. $6.4\times {10}^{-13}$ $\mathrm{J}$

Fission of nuclei is possible because the binding energy per nucleon in them:

${}_{10}{}^{22}\mathrm{Ne}$ nucleus after absorbing energy decays into two \(\alpha- \text{particle}\) and an unknown nucleus. The unknown nucleus is:

1. Nitrogen

2. Carbon

3. Boron                 

4. Oxygen

An atomic nucleus ${}_{90}{}^{232}\mathrm{Th}$ emits several $\mathrm{\alpha }$ and $\mathrm{\beta }$ radiations and finally reduces to ${}_{82}{}^{208}\mathrm{Pb}$. It must have emitted:
1. 4$\mathrm{\alpha }$ and 2$\mathrm{\beta }$             
2. 6$\mathrm{\alpha }$ and 4$\mathrm{\beta }$
3. 8$\mathrm{\alpha }$ and 24$\mathrm{\beta }$           
4. 4$\mathrm{\alpha }$ and 16$\mathrm{\beta }$

During negative $\mathrm{\beta }$-decay:

In nuclear reaction ${}_2{}^4\mathrm{He}+{}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}\to {}_{\mathrm{Z}+2}{}^{\mathrm{A}+3}\mathrm{Y}+\mathrm{B}$, \(\mathrm {B}\) denotes:

1. Electron           

2. Positron

3. Proton               

4. Neutron

The mass of an $\mathrm{\alpha }$-particle is:

The rest energy of an electron is:

The Binding energy per nucleon of \(^{7}_{3}\mathrm{Li}\) and \(^{4}_{2}\mathrm{He}\) nucleon are \(5.60~\text{MeV}\) and \(7.06~\text{MeV}\), respectively. In the nuclear reaction \(^{7}_{3}\mathrm{Li} + ^{1}_{1}\mathrm{H} \rightarrow ^{4}_{2}\mathrm{He} + ^{4}_{2}\mathrm{He} +Q\), the value of energy \(Q\) released is:
1. \(19.6~\text{MeV}\)
 2. \(-2.4~\text{MeV}\)
 3. \(8.4~\text{MeV}\)
4. \(17.3~\text{MeV}\)

A nucleus \({ }_{{n}}^{{m}} {X}\) emits one $\mathrm{}$\(\alpha\text -\text{particle}\) and two \(\beta\text- \text{particle}\) The resulting nucleus is:
1. \(^{m-}{}_n^6 Z \)
2. \(^{m-}{}_{n}^{4} X \)
3. \(^{m-4}_{n-2}Y\)
4. \(^{m-6}_{n-4} Z \)