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. ${}_{77}\mathrm{Y}_{289}$

Thermal neutrons can cause fission in 

(1) ${\mathrm{U}}^{235}$          

(2) ${\mathrm{U}}^{238}$

(3) ${\mathrm{Pu}}^{238}$        

(4) ${\mathrm{Th}}^{232}$

When neutrons are bombarded on nucleus of ${}_{92}\mathrm{U}_{235}$, the number of emitted neutrons will be 

(1) 1         

(2) 2

(3) 3         

(4) 4