In nuclear reaction \({}_{2}^{4}\mathrm{He}+ {}_{Z}^{A}\mathrm{X}\rightarrow {}_{Z+2}^{A+3}\mathrm{X}+\mathrm{B},\) \(\mathrm {B}\) denotes:
1. electron
2. positron
3. proton
4. neutron

Energy generation in stars is mainly due to

(1) Chemical reactions               

(2) Fission of heavy nuclei

(3) Fusion of light nuclei             

(4) Fusion of heavy nuclei

Fusion reaction is initiated with the help of 

(1) Low temperature         

(2) High temperature

(3) Neutrons                     

(4) Any particle

When a ${}_4{}^9\mathrm{Be}$ atom is bombarded with $\mathrm{\alpha }$ particles, one of the product of nuclear transmutation is ${}_6{}^{12}\mathrm{C}$. The other is 

(1) ${}_{-1}{}^0\mathrm{e}$           

(2) ${}_1{}^1\mathrm{H}$

(3) ${}_1{}^2\mathrm{D}$            

(4) ${}_0{}^1\mathrm{n}$

During the nuclear fusion reaction 

(1) A heavy nucleus breaks into two fragments by itself

(2) A light nucleus bombarded by thermal neutrons breaks up

(3) A heavy nucleus bombarded by thermal neutrons breaks up

(4) Two light nuclei combine to give a heavier nucleus and  possibly other products

A gamma ray photon creates an electron- positron pair. If the rest mass energy of an electron is 0.5 MeV and the total K.E. of the electron- positron pair is 0.78 MeV, then the energy of the gamma ray photon must be 

(1) 0.78 MeV                 

(2) 1.78 MeV

(3) 1.28 MeV                 

(4) 0.28 MeV

Which of the following statement is true 

(1) ${}_{78}\mathrm{Pt}_{192}$ has 78 neutrons

(2) ${}_{84}\mathrm{Po}_{214}\to {}_{82}\mathrm{Pb}_{210}+{\mathrm{\beta }}^{-}$

(3) ${}_{92}U_{238}\to {}_{90}\mathrm{Th}_{234}+{}_2\mathrm{He}_4$

(4) ${}_{90}\mathrm{Th}_{234}\to {}_{91}\mathrm{Pa}_{234}+{}_2\mathrm{He}_4$

Fast neutrons can easily be slowed down by 

(1) The use of lead shielding

(2) Passing them through heavy water

(3) Elastic collisions with heavy nuclei

(4) Applying a strong electric field

When ${}_{92}\mathrm{U}_{235}$ undergoes fission, 0.1% of its original mass is changed into energy. How much energy is released if 1kg of ${}_{92}\mathrm{U}_{235}$ undergoes fission

(1) $9\times {10}^{10} \mathrm{J}$           

(2)  $9\times {10}^{11} \mathrm{J}$

(3) $9\times {10}^{12} \mathrm{J}$           

(4) $9\times {10}^{13} \mathrm{J}$

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

(1) 5.0 MeV               

(2) 4.02 MeV

(3) 15.0 MeV               

(4) 1.02 MeV