Nuclear fission experiments show that the neutrons split the uranium nuclei into two fragments of about same size. This process is accompanied by the emission of several
Heavy water is used as moderator in a nuclear reactor. The function of the moderator is(a) To control the energy released in the reactor(b) To absorb neutrons and stop chain reaction(c) To cool the reactor faster(d) To slow down the neutrons to thermal energies
In a fission process, nucleus $A$ divides into two nuclei $B$ and $C ,$ their binding energies being $\mathrm{E}_{\mathrm{a}}, \mathrm{E}_{\mathrm{b}}$ and $\mathrm{E}_{\mathrm{c}}$ respectively. Then
Thermal neutrons are those which(a) Are at very high temperature(b) Move with high velocities(c) Have kinetic energies similar to those of surrounding molecules (d) Are at rest
Answer
(c) Have kinetic energies similar to those of surrounding molecules
Energy released in the fission of a single $92^{\mathrm{U}^{235}}$ nucleus is $200\ \text{MeV}.$The fission rate of a $92^{\mathrm{U}^{235}}$ fuelled reactor operating at a power level of $5W$ is
In nuclear fission, the fission reactions proceeds with a projectile. Which of the following suits the best(a) Slow proton(b) Fast neutron(c) Slow neutron(d) None of these
The example of nuclear fusion is(a) Formation of barium and krypton from uranium(b) Formation of helium from hydrogen(c) Formation of plutonium 235 from uranium 235(d) Formation of water from hydrogen and oxygen
If $200\ \text{MeV}$ 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 $1eV = 1.6 \times 10^{-19} J) $
In the nuclear reaction $92^{\mathrm{U}^{2 \mathrm{~s}}} \rightarrow \mathrm{z}^{\mathrm{Th}^{\mathrm{A}}}+2^{\mathrm{He}^4}$, the values of $A$ and $Z$ are
$200\ MeV$ of energy may be obtained per fission of $U^{235}$. A reactor is generating $1000\ kW$ of power. The rate of nuclear fission in the reactor is
γ-rays radiation can be used to create electron-positron pair. In this process of pair production, γ-rays energy cannot be less than(a) 5.0 MeV(b) 4.02 MeV(c) 15.0 MeV(d) 1.02 MeV
Fast neutrons can easily be slowed down by(a) The use of lead shielding(b) Passing them through water(c) Elastic collisions with heavy nuclei(d) Applying a strong electric field
A nuclear bomb exploded 200 km above the surface of moon. The sound of explosion on the moon(a) Will heard before the explosion is seen(b) Will be heard at the same time(c) Will be heard after explosion(d) Will not heard at all
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(a) 0.78 MeV(b) 1.78 MeV(c) 1.28 MeV(d) 0.28 MeV
The mechanism of the hydrogen bomb is based on(a) Fission of isotopes of hydrogen(b) Fusion of protons(c) Fusion of deutrium and tritium(d) Fusion of neutrons
When $_{92}U^{235}$ undergoes fission, $0.1\%$ of its original mass is changed into energy. How much energy is released if $1\ kg$ of $_{92}U^{235}$ undergoes fission
Fusion reaction takes place at high temperature because(a) Atoms are ionised at high temperature(b) Molecules break-up at high temperature(c) Nuclei break-up at high temperature (d) Kinetic energy is high enough to overcome repulsion between nuclei
Answer
(d) Kinetic energy is high enough to overcome repulsion between nuclei
In a working nuclear reactor, Cadmium rods, (control rods) are used to(a) Speed up neutrons(b) Slow down neutrons(c) Absorb some neutrons(d) Absorb all neutrons
During the nuclear fusion reaction(a) A heavy nucleus breaks into two fragments by itself(b) A light nucleus bombarded by thermal neutrons breaks up(c) A heavy nucleus bombarded by thermal neutrons breaks up(d) Two light nuclei combine to give a heavier nucleus and possibly other products
Answer
(d) Two light nuclei combine to give a heavier nucleus and possibly other products
If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction(a) 2/3(b) 4/9(c) 3/4(d) 5/9
An $a-$particle of $5\ MeV$ energy strikes with a nucleus of uranium at stationary at an scattering angle of $180^\circ$. The nearest distance upto which $a-$particle reaches the nucleus will be of the order of