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

A reaction between a proton and ${}_8\mathrm{O}_{18}$ that produces ${}_9\mathrm{F}_{18}$ must also liberate 

(1) ${}_0\mathrm{n}_1$         

(2) ${}_1\mathrm{e}_0$

(3) ${}_1\mathrm{n}_0$         

(4) ${}_0\mathrm{e}_1$

In the nuclear reaction ${}_{92}\mathrm{U}_{238}\to {}_{\mathrm{z}}\mathrm{Th}_{\mathrm{A}}+{}_2\mathrm{He}_4$ , the values of A and Z are

(1) A = 234, Z = 94             

(2) A = 234, Z = 90

(3) A = 238, Z = 94             

(4) A = 238, Z = 90

If 200 MeV energy is released in the fission of a single ${\mathrm{U}}^{235}$ nucleus, the number of fissions required per second to produce 1 kilowatt power shall be (Given

$1 \mathrm{eV}=1.6\times {10}^{-19} \mathrm{J}$) 

(1) $3.125\times {10}^{13}$         

(2) $3.125\times {10}^{14}$

(3) $3.125\times {10}^{15}$           

(4) $3.125\times {10}^{16}$

In nuclear fission, the fission reactions proceeds with a projectile. Which of the following suits the best

(1) Slow proton             

(2) Fast neutron

(3) Slow neutron         

(4) None of these

In the nuclear reaction  ${}_{85}{}^{297}\mathrm{X}\to \mathrm{Y}+4\mathrm{\alpha }$, Y is 

1. ${}_{76}\mathrm{Y}_{287}$            

2. ${}_{77}\mathrm{Y}_{285}$

3. ${}_{77}\mathrm{Y}_{281}$             

4. ${}_{77}\mathrm{Y}_{289}$