All exercise Short Questions of Nuclear Reactions of book Nuclear Physics for BS/MSc Physics students.
Q.1 What is a nuclear reaction simple definition?
Answer. Nuclear reaction. A process, such as fission, fusion, or radioactive decay, in which the structure of an atomic nucleus is altered through release of energy or mass or by being broken apart.
Q.2 What is an example of a nuclear reaction?
Answer. Some examples include: Fusion reactions — two light nuclei join to form a heavier one, with additional particles (usually protons or neutrons) emitted subsequently. … This is an induced nuclear reaction. Spontaneous fission, which occurs without assistance of a neutron, is usually not considered a nuclear reaction.
Q.3 How does a nuclear reaction work?
Answer. Nuclear energy originates from the splitting of uranium atoms – a process called fission. This generates heat to produce steam, which is used by a turbine generator to generate electricity. Because nuclear power plants do not burn fuel, they do not produce greenhouse gas emissions.
Q.4 What happens in a nuclear reaction?
Answer. A nuclear reaction is at its most basic nothing more than a reaction process that occurs in an atomic nucleus. They typically take place when a nucleus of an atom gets smacked by either a subatomic particle (usually a “free neutron,” a short-lived neutron not bound to an existing nucleus) or another nucleus.
Q.5 Which is a characteristic of a nuclear reaction?
Answer. Nuclear reaction, change in the identity or characteristics of an atomic nucleus, induced by bombarding it with an energetic particle.
Q.6 Is transmutation a nuclear reaction?
Answer. A transmutation can be achieved either by nuclear reactions (in which an outside particle reacts with a nucleus) or by radioactive decay, where no outside cause is needed. … Artificial transmutation may occur in machinery that has enough energy to cause changes in the nuclear structure of the elements.
Q.7 What is the difference between nuclear reaction and chemical reaction?
Answer. Major differences between nuclear and chemical reactions
(1) Nuclear reactions involve a change in an atom’s nucleus, usually producing a different element. Chemical reactions, on the other hand, involve only a rearrangement of electrons and do not involve changes in the nuclei.
Q.8 Is Matter destroyed in a nuclear reaction?
Answer. No. Matter isn’t destroyed in nuclear reactions. Matter is only destroyed or annihilated when it meets antimatter. In nuclear reactions either a fission or fusion occurs, in both processes releasing vast amounts of energy as new elements are created.
Q.9 What is conserved in a nuclear reaction?
Answer. In both nuclear and chemical reactions, two physical quantities are seen to be conserved and unchanging: the number of particles and the total charge. A constant number of particles in nuclear reactions does not imply that mass is conserved.
Q.10 How is resonance in nuclear reaction obtained?
Answer. Nuclear reaction analysis. … To contribute to the nuclear reaction the projectile nuclei have to slow down in the sample to reach the resonance energy. Thus each initial kinetic energy corresponds to a depth in the sample where the reaction occurs (the higher the energy, the deeper the reaction).
Q.11 Why does nuclear decay occur?
Answer. Radioactive decay occurs in unstable atomic nuclei – that is, ones that don’t have enough binding energy to hold the nucleus together due to an excess of either protons or neutrons. It comes in three main types – named alpha, beta and gamma for the first three letters of the Greek alphabet.
Q.12 What went wrong in Chernobyl?
Answer. Chernobyl Accident 1986. The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel. The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the atmosphere and downwind – some 5200 PBq (I-131 eq).
Q.13 What is the meaning of cross-sectional area?
Answer. The Cross section of an object is the shape you get when you cut straight through an object. … Cross section of the cylinder perpendicular to its axis is a circle. Hence the cross sectional area is the area of a circle.
Q.14 What is total cross section?
Answer. Cross section (physics) … When a cross section is specified as a function of some final-state variable, such as particle angle or energy, it is called a differential cross section. When a cross section is integrated over all scattering angles (and possibly other variables), it is called a total cross section.
Q.15 What is macroscopic cross section?
Answer. While the macroscopic cross–section represents the effective target area of all of the nuclei contained in the volume of the material. The units are given in cm-1. A macroscopic cross–section is derived from microscopic cross–section and the atomic number density: Σ=σ.N.
Q.16 How do you describe a cross section?
Answer. The intersection of a solid and a plane is called a cross section of the solid. Describe the shape resulting from a vertical, angled, and horizontal cross section of a cylinder. The cross section is a rectangle. The cross section is an oval.
Q.17 What is the scattering cross section?
Answer. Scattering cross–sections. A scattering cross–section, σ, is a quantity proportional to the rate at which a particular radiation–target interaction occurs. … Dimensionally, a cross–section represents an area, with the basic unit being the barn, which represents an area of 10−28 m 2.
Q.18 What is the differential cross section?
Answer. Differential (scattering) cross section. … The differential (scattering) cross section is defined as the ratio of the intensity of radiant energy scattered in a given direction to the incident irradiance and thus has dimensions of area per unit solid angle.
Q.19 What is capture cross section?
Answer. Capture cross section
The absorption neutron cross–section of an isotope of a chemical element is the effective cross sectional area that an atom of that isotope presents to absorption, and is a measure of the probability of neutron capture. It is usually measured in barns (b).
Q.20 What is meant by neutron cross section?
Answer. In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. … Some isotopes, like uranium-238, have nonzero cross sections of all three.
Q.21 Can the cross section of a solid ever be a point?
Answer. Cross section: When a plane intersects a solid figure, the cross-sectional face may be a point, a line segment, or a two-dimensional shape such as, but not limited to, a circle, rectangle, oval, or hexagon. … The plane may, or may not, be parallel to the base of the figure.
Q.22 What is the cross section of a cone?
Answer. (1) Any cross section of a sphere is a circle. (2) A horizontal cross section of a cone is a circle, while its vertical cross section is a triangle. (3) The horizontal cross section of a cylinder is circle and the vertical cross section is a rectangle.
Q.23 What is the cross section of a sphere?
Answer. The surface of a sphere is perfectly round. Note: A “sphere” is the outer surface of a “ball” (or “solid sphere“). … Such a circle will be found when the cross–sectional plane passes through the center of the sphere.
Q.24 What do you mean by compound nucleus?
Answer. Compound Nucleus. a nuclear system formed in the course of a nuclear reaction by the combination of the incident particle with the target nucleus. A compound nucleus is unstable and decays after a short period into final reaction products. … The notion of the compound nucleus was first advanced by N. Bohr in 1936.
Q.25 How compound nucleus is formed?
Answer. The compound nucleus is the intermediate state formed in a compound nucleus reaction. It is normally one of the excited states of the nucleus formed by the combination of the incident particle and target nucleus.
Q.26 What is direct reaction?
Answer. A reaction is called direct if it proceeds directly. from the initial to the final state without the. formation of an intermediate compound nucleus. (it takes place in one or “a few” steps) Direct reactions are fast, compound reactions.
Q.27 What are stripping and pick up reaction?
Answer. Stripping reaction in which one or more nucleons are transferred to a target nucleus from passing particle. For example the neutron stripping in the (d, p) reaction. Pick–up reaction in which one or more nucleons are transferred from a target nucleus to a passing particle.
Q.28 What is the significance of Q- value equation?
Answer. The Q value of the reaction denotes the energy released or absorbed in a reaction. This gives a physical verification of conversion of mass into kinetic energy and vice versa. For an exothermic reaction Q>0 i.e., the process is accompanied by the liberation of energy. For an endothermic reaction Q<0 i.e., the process is accompanied by the absorption of energy.
Q.29 What is Q- value of a nuclear reaction known as elastic scattering?
Answer. For elastic scattering, nuclear reaction can be written as,
a + X $\rightarrow$ a + X
Therefore Q-value is,
Q = (TX + Ta) – ((TX + Ta) = 0
The Q- value for elastic scattering is zero.
Q.30 What is meant by nuclear reaction kinematics?
Answer. At any energy, the conservation of energy and momentum imposes certain restrictions on the nuclear reactions. These restrictions are called kinematics restrictions and its mathematical method is known as nuclear reaction kinematics.
Q.31 Differentiate between compound nucleus reactions and direct nuclear reactions.
Answer.
| Compound nucleus reactions | Direct nuclear reaction |
| Compound nuclear reactions take place in a very long time ~ 10-16 – 1018 sec | Direct nuclear reactions take place in a small time ~ 10-22 s. |
| Reaction induced by neutron can be processed by compound nucleus reaction as well as direct nuclear reaction | ii) Reaction induced by protons can be processed only through direct mechanism. |
Q.32 For which of the following target nuclei ZXA do you expect the reaction to be the strongest and why?
ZXA = 20Ca39 , 20Ca40 , 20Ca41
Answer. The reaction is strongest with a target of 20Ca41. In the reaction the proton combines with a neutron in 20Ca41 to form a deuteron. The isotope 20Ca41 has an excess neutron outside of double-full shell, which means that the binding energy of the last neutron is lower than those of 20Ca39 20Ca40 and so it is easier to pick up.
Q.33 Which one is value of typical cross section for low energy neutron – nucleus scattering out of 10-16 , 10-24, 10-32 , 10-40 cm2?
Answer. The typical cross section for low energy neutron-nucleus scattering is 10-24 cm2. The radius of the sphere of action of nuclear forces is ~ 10-12 – 10-13 cm and a typical scattering cross-section can be expected to be of the same order of magnitude as its cross – sectional area.
Q.34 Assume the neutrino mass is exactly zero. Does the neutrino have a magnetic moment? Along what direction (s) does the neutrino spin point? Along what direction(s) does the antineutrino spin point?
Answer. If the neutrino masses are strictly zero, they have no magnetic moment. The neutrino spin points along a direction opposite to its motion, while the antineutrino spin does the reverse.
Q.35 How many neutrino types are known to exist? What is the spin of a neutrino?
Answer. Two kinds of neutrino have been found so far. These are electron – neutrino sand Muons-neutrinos and their antiparticles. Theory predicts the existence of a third kind of neutrino, – neutrino and its antiparticle. The neutrino spin is 1/ 2.
Q.36 How do you expect the neutron elastic scattering cross section to depend on energy for very low energy neutrons?
Answer. For thermal neutron of very low energies, the elastic scattering cross-section of light nuclei does not depend on the neutron energy, but is constant for a large range of energy. But for heavier nuclei, resonant scattering can occur in some cases at very low neutron energies. For instance, resonant scattering with 64Gd157 occurs at En = 0.044eV.
Q.37 What properties of neutrinos are conserved in scattering processes? What is the difference between a neutrino and antineutrino?
Answer. In scattering process, the lepton number of each kind of neutrinos conserved. The difference between a neutrino and the corresponding antineutrino is that they have opposite lepton numbers. Furthermore, if the neutrino mass is zero, the velocities of neutrino and antineutrino are opposite.
