The half life of radioactive Radon is 3.8 days. The time at the end of which 1/20 th of the Radon sample will remain undecayed is
(Given ${\log }_{10}\mathrm{e}=0.4343$) 
(a) 3.8 days               (b) 16.5 days
(c) 33 days                (d) 76 days

For uranium nucleus how does its mass vary with volume

(1) $\mathrm{m}\propto \mathrm{V}$          

(2) $\mathrm{m}\propto 1/\mathrm{V}$

(3) $<mspace\; width="1em"></mspace>\mathrm{m}\propto \sqrt{\mathrm{V}}$       

(4) $\mathrm{m}\propto {\mathrm{V}}^2$

A nucleus with mass number 220 initially at rest emits an $\mathrm{\alpha }$-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the $\mathrm{\alpha }$-particle

(1) 4.4 MeV             

(2) 5.4 MeV

(3) 5.6 MeV             

(4) 6.5 MeV

The binding energy per nucleon of ${\mathrm{O}}^{16}$ is 7.97 MeV and that of ${\mathrm{O}}^{17}$ is 7.75 MeV. The energy (in MeV) required to remove a neutron from ${\mathrm{O}}^{17}$ is 
(a) 3.52                 (b) 3.64
(c) 4.23                 (d) 7.86

In the nuclear fusion reaction ${}_1{}^2\mathrm{H}+{}_1{}^3\mathrm{H}\to {}_2{}^4\mathrm{He}+\mathrm{n}$ given that the repulsive potential energy between the two nuclei is $-7.7\times {10}^{-14}<mspace\; width="1em"></mspace>\mathrm{J}$, the temperature at which the gases must be heated to initiate the reaction is nearly
[Boltzmann’s constant $\mathrm{k}=1.38\times {10}^{-23}<mspace\; width="1em"></mspace>\mathrm{J}/\mathrm{K}$)
(a)${10}^9<mspace\; width="1em"></mspace>\mathrm{K}$            (b) ${10}^7<mspace\; width="1em"></mspace>\mathrm{K}$
(c) ${10}^5<mspace\; width="1em"></mspace>\mathrm{K}$           (d)  ${10}^3<mspace\; width="1em"></mspace>\mathrm{K}$

If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately
(1) 60%             

(2) 65%

(3) 70%             

(4) 75%

The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be
(1) 0.026 MeV           

(2) 0.051 MeV

(3) 0.079 MeV           

(4) 0.105 MeV

The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is 1.4 $\mathrm{kilowatt}/{\mathrm{m}}^2$.The average earth- sun distance is $1.5\times {10}^{11}$ metres. The mass lost by the sun per day is
(1 day = 86400 seconds) 
(a) $4.4\times {10}^9<mspace\; width="1em"></mspace>\mathrm{kg}$          (b) $7.6\times {10}^{14}<mspace\; width="1em"></mspace>\mathrm{kg}$
(c) $3.8\times {10}^{12}<mspace\; width="1em"></mspace>\mathrm{kg}$         (d) $3.8\times {10}^{14}<mspace\; width="1em"></mspace>\mathrm{kg}$

A neutron with velocity V strikes a stationary deuterium atom. Its kinetic energy changes by a factor of 
(1) $\frac{15}{16}$             

(2) $\frac{1}{2}$

(3) $\frac{2}{1}$               

(4) None of these