HC Verma Physics books are the most preferred books among students of CBSE schools. Students can be found referring to the chapters as well as practice questions at the end of each of these chapters, in the books. Students follow these textbooks religiously since quite a few questions in these also appear in exams.<\/p>\n\n\n\n
For such popular books, students can get extremely helpful practice material online. For all the questions in the HC Verma books, there are several sources where students can get detailed solutions and solve their doubts and queries.<\/p>\n\n\n\n
Please note that these solutions are provided here for free.<\/p>\n\n\n\n
If neutrons exert only attractive force, why don\u2019t we have a nucleus containing neutrons alone?<\/p>\n\n\n\n
Nuclear forces are short range strong attractive forces that act between two proton-proton, neutron-proton and neutron-neutron pairs. Two protons have strong nuclear forces between them and also exert electrostatic repulsion on each other. However, electrostatic forces are long ranged and have very less effect as compared to the strong nuclear forces.
So, in a nucleus (that is very small in dimension), there\u2019s no such significance of repulsive force as compared to the strong attractive nuclear force. On the other hand, an atom contains electrons revolving around its nucleus. These electrons are kept in their orbit by the strong electrostatic force that is exerted on them by the protons present inside the nucleus. Hence, a nucleus contains protons as well as neutrons.<\/p>\n\n\n\n
Consider two pairs of neutrons. In each pair, the separation between the neutrons is the same. Can the force between the neutrons have different magnitudes for the two pairs?<\/p>\n\n\n\n
Neutrons are chargeless particles and they exert only short range nuclear forces on each other. If we have two pairs of neutrons and the separation between them is same in both the pairs. The force between the neutrons will be of same magnitude for the two pairs until there is some other influence on any of them.<\/p>\n\n\n\n
A molecule of hydrogen contains two protons and two electrons. The nuclear force between these two protons is always neglected while discussing the behaviour of a hydrogen molecule. Why?<\/p>\n\n\n\n
Inside the nucleus, two protons exert nuclear force on each other. These forces are short-ranged (a few fm), strong and attractive forces. They also exert electrostatic repulsive force (long-ranged). While discussing the behaviour of a hydrogen molecule, the nuclear force between the two protons is always neglected. This is because the separation between the two protons in the molecule is<\/p>\n\n\n\n
~70 pm which is much greater than the range of the nuclear force.<\/p>\n\n\n\n
Is it easier to take out a nucleon (a) from carbon or from iron (b) from iron or from lead?<\/p>\n\n\n\n
Binding energy per nucleon of a nucleus is defined as the energy required to break-off a nucleon from it.
(a) As the binding energy per nucleon of iron is more than that of carbon, it is easier to take out a nucleon from carbon than iron.
(b) As the binding energy per nucleon of iron is more than that of lead. Therefore, it is easier to take out a nucleon from lead as compared to iron.<\/p>\n\n\n\n
Suppose we have 12 protons and 12 neutrons. We can assemble them to form either a 24<\/sup>Mg nucleus or two 12<\/sup>C nuclei. In which of the two cases more energy will be liberated?<\/p>\n\n\n\n If we assemble 6 protons and 6 neutrons to form 12<\/sup>C nucleus, 92.15 MeV (product of mass number and binding energy per nucleon of carbon-12) of energy is released. Therefore, the energy released in the formation of two carbon nuclei is 184.3 MeV. On the other hand, when 12 protons and 12 neutrons are combined to form a 24<\/sup>Mg atom, 198.25 MeV of energy (binding energy) is released. Hence, in case of \u00e2\u20ac\u203924<\/sup>Mg nucleus, more energy is liberated.<\/p>\n\n\n\n What is the difference between cathode rays and beta rays? When the two are travelling in space, can you make out which is the cathode ray and which is the beta ray?<\/p>\n\n\n\n Cathode rays consist of electrons that are accelerated using electrodes. They do not carry high energy and do not harm human body. On the other hand, beta rays consist of highly energetic electrons that can even penetrate and damage human cells. Beta rays are produced by the decay of radioactive nuclei. If the two are travelling in space, they can be distinguished by the phenomenon named production of Bremsstrahlung radiation, which is produced by the deceleration of a high energy particle when deflected by another charged particle, leading to the emission of blue light. Only beta rays are capable of producing it.<\/p>\n\n\n\n If the nucleons of a nucleus are separated from each other, the total mass is increased. Where does this mass come from?<\/p>\n\n\n\n When the nucleons of a nucleus are separated, a certain amount of energy is to be given to the nucleus, which is known as the binding energy. \u00d7(Mass of a nucleon) \u2013 (Mass of the nucleus)]<\/p>\n\n\n\n When the nucleons of a nucleus are separated, the increase in the total mass comes from the binding energy, which is given to the nucleus to break-off its constituent nucleons as energy is related to mass by the relation given below. In beta decay, an electron (or a positron) is emitted by a nucleus. Does the remaining atom get oppositely charged?<\/p>\n\n\n\n In beta decay, a neutron from the nucleus is converted to a proton releasing an electron and an antineutrino or a proton is converted to a neutron releasing a positron and a neutrino.<\/p>\n\n\n\n i.e. \u03b2- decay: n\u2192p+e+\u03bd\u00af\u03b2+ decay: p\u2192n+e++\u03bdSince the number of valence electrons present in the parent atom do not change, the remaining atom does not get oppositely charged. Instead, due to a change in the atomic number, there\u2019s a formation of a new element.<\/p>\n\n\n\n When a boron nucleus<\/p>\n\n\n\n (B510)is bombarded by a neutron, a \u03b1-particle is emitted. Which nucleus will be formed as a result?<\/p>\n\n\n\n It is given that when a boron nucleus<\/p>\n\n\n\n (B510)is bombarded by a neutron, an \u03b1-particle is emitted.<\/p>\n\n\n\n Let X<\/em> nucleus be formed as a result of the bombardment. B510+n01\u2192X+H24eCharge: 5 0 3 2Mass: 10 1 7 4The mass number of X should be 7 and its atomic number should be 3.<\/p>\n\n\n\n \u2234X=L37i<\/p>\n\n\n\n Does a nucleus lose mass when it suffers gamma decay?<\/p>\n\n\n\n Gamma rays consist of photons that are produced when a nucleus from its excited state comes to its ground state releasing energy. Since gamma rays are chargeless and massless particles, the nucleus does not suffer any loss in mass during the gamma decay.<\/p>\n\n\n\n In a typical fission reaction, the nucleus is split into two middle-weight nuclei of unequal masses. Which of the two (heavier or lighter) has greater kinetic energy? Which one has greater liner momentum?<\/p>\n\n\n\n Two photons having equal liner momentum have equal wavelengths as here for both the photons the direction and magnitude of linear momentum will be same. For the rest of the options, magnitude will be same but nothing can be said about the direction of the photons. If three helium nuclei combine to form a carbon nucleus, energy is liberated. Why can\u2019t helium nuclei combine on their own and minimise the energy?<\/p>\n\n\n\n When three helium nuclei combine to form a carbon nucleus, energy is liberated. This energy is greater than the that liberated when these nuclei combine on their own. Hence, formation of carbon nucleus leads to much more stability as compared to the combination of three helium nuclei.<\/p>\n\n\n\n The mass of a neutral carbon atom in ground state is (a) exact 12 u<\/p>\n\n\n\n In nuclear physics, a unit used for measurement of mass is unified atomic mass unit, which is denoted by u.<\/p>\n\n\n\n It is defined such that<\/p>\n\n\n\n 1 u =<\/p>\n\n\n\n 112\u00d7(Mass of neutral carbon atom in its ground state)<\/p>\n\n\n\n Mass of neutral carbon atom in its ground state = 12 \u00d7 1 u = 12 u<\/p>\n\n\n\n Thus, the mass of neutral carbon atom in its ground state is exactly 12 u.<\/p>\n\n\n\n The mass number of a nucleus is equal to (c) the number of nucleons in the nucleus<\/p>\n\n\n\n Mass number of a nucleus is defined as the sum of the number of neutron and protons present in the nucleus, i.e. the number of nucleons in the nucleus.<\/p>\n\n\n\n As compared to 12<\/sup>C atom, 14<\/sup>C atom has (c) two extra neutrons and no extra electron<\/p>\n\n\n\n 12<\/sup>C and 14<\/sup>C are the two isotopes of carbon atom that have same atomic number, but different mass numbers. This means that they have same number of protons and electrons, but different number of neutrons. Therefore, \u00e2\u20ac\u203912\u00e2\u20ac\u2039<\/sup>C has 6 protons, 6 electrons and 6 neutrons, whereas \u00e2\u20ac\u203914<\/sup>C has 6 electrons, 6 protons and 8 neutrons.<\/p>\n\n\n\n The mass number of a nucleus is (d) sometimes more than and sometimes equal to its atomic number<\/p>\n\n\n\n Mass number of a nucleus is defined as the sum of the number of neutron and protons present in the nucleus, i.e. the number of nucleons in the nucleus, whereas atomic number is equal to the number of protons present. Therefore, the atomic number is smaller than the mass number. But in the nucleus (like that of hydrogen 1<\/sup>H\u00e2\u20ac\u20391<\/sub>), only protons are present. Due to this, the mass number is equal to the atomic number.<\/p>\n\n\n\n The graph of ln(R<\/em>\/R<\/em>0<\/sub>) versus ln A<\/em>(R<\/em> = radius of a nucleus and A<\/em> = its mass number) is (a) a straight line R=RoA13RRo=A13lnRRo=13ln ATherefore, the graph of ln(R\/<\/em>R<\/em>0) versus ln A<\/em> is a straight line passing through the origin with slope 1\/3.<\/p>\n\n\n\n Let Fpp<\/sub><\/em>, Fpn<\/sub><\/em> and Fnn<\/sub><\/em> denote the magnitudes of the net force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron respectively. neglect gravitational force. When the separation is 1 fm. (d) F<\/em>pp < F<\/em>pn = F<\/em>nn<\/p>\n\n\n\n Protons and neutrons are present inside the nucleus and they exert strong attractive nuclear forces on each other, which are equal in magnitude. Due to their positive charge, protons repel each other. Hence the net attractive force between two protons gets reduced, but the nuclear force is stronger than the electrostatic force at a separation of 1 fm.<\/p>\n\n\n\n \u2234 F<\/em>pp < F<\/em>pn = F<\/em>nn<\/p>\n\n\n\n Here, F<\/em>pp, F<\/em>pn and F<\/em>nn denote the magnitudes of the net force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron, respectively.<\/p>\n\n\n\n Let Fpp<\/sub><\/em>, Fpn<\/sub><\/em> and Fnn<\/sub><\/em> denote the magnitudes of the nuclear force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron respectively. When the separation is 1 fm, (b) F<\/em>pp<\/sub> = F<\/em>pn<\/sub> = F<\/em>nn<\/sub><\/p>\n\n\n\n Protons and neutrons are present inside the nucleus and they exert strong attractive nuclear force on each other. These forces are equal in magnitude, irrespective of the charge present on the nucleons.<\/p>\n\n\n\n \u2234 F<\/em>pp<\/sub> = F<\/em>pn<\/sub> = F<\/em>nn<\/sub> Two protons are kept at a separation of 10 nm. Let Fn<\/sub><\/em> and Fe<\/sub><\/em> be the nuclear force and the electromagnetic force between them. (b) F<\/em>e<\/sub> >> F<\/em>n<\/sub><\/p>\n\n\n\n Two protons exert strong attractive nuclear force and repulsive electrostatic force on each other. Nuclear forces are short range forces existing in the range of a few fms. Therefore, at a separation of 10 nm, the electromagnetic force is greater than the nuclear force, i.e. F<\/em>e<\/sub> >> F<\/em>n<\/sub>. <\/em><\/p>\n\n\n\n As the mass number A<\/em> increases, the binding energy per nucleon in a nucleus (d) varies in a way that depends on the actual value of A<\/p>\n\n\n\n Binding energy per nucleon in a nucleus first increases with increasing mass number (A) and reaches a maximum of 8.7 MeV for A<\/em> (50\u221280). Then, again it slowly starts decreasing with the increase in A and drops to the value of 7.5 MeV.<\/p>\n\n\n\n Which of the following is a wrong description of binding energy of a nucleus? (d) It is the sum of the kinetic energies of all the nucleons present in the nucleus.<\/p>\n\n\n\n Binding energy of a nucleus is defined as the energy required to break the nucleus into its constituents. It is also measured as the Q<\/em>-value of the breaking of nucleus, i.e. the difference between the rest energies of reactants (nucleus) and the products (nucleons) or the difference between the kinetic energies of the products and the reactants.<\/p>\n\n\n\n In one average-life, (c) more than half the active nuclei decay<\/p>\n\n\n\n The average life is the mean life time for a nuclei to decay. \u03c4=1\u03bb=\u03a4120.693Here,<\/p>\n\n\n\n \u03c4, \u03bb and \u03a412 are the average life, decay constant and half life-time of the active nuclei, respectively. The value of the average lifetime comes to be more than the average lifetime. Therefore, in one average life, more than half the active nuclei decay.<\/p>\n\n\n\n In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following particles is emitted in the decay? (d) Photon<\/p>\n\n\n\n The atomic number and mass number of a nucleus is defined as the number of protons and the sum of the number of protons and neutrons present in the nucleus, respectively. Since in the decay, neither the atomic number nor the mass number change, it cannot be a beta-decay (release of electron, proton or neutron). Hence, the particle emitted can only be a photon.<\/p>\n\n\n\n During a negative beta decay, (c) a neutron in the nucleus decays emitting an electron<\/p>\n\n\n\n Negative beta decay is given as<\/p>\n\n\n\n n\u2192p+e-+\u03bd\u00af A freshly prepared radioactive source of half-life 2 h emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is (b) 12 h<\/p>\n\n\n\n A freshly prepared radioactive source emits radiation of intensity that is 64 times the permissible level. This means that it is possible to work safely till 6 half-lives (as 26<\/sup> = 64) of the radioactive source. Since the half-life of the source is 2h, the minimum time after which it would be possible to work safely with this source is 12 h.<\/p>\n\n\n\n The decay constant of a radioactive sample is \u03bb. The half-life and the average-life of the sample are respectively (b) (ln 2\/\u03bb) and 1\/\u03bb<\/p>\n\n\n\n The half-life of a radioactive sample (<\/p>\n\n\n\n t12) is defined as the time elapsed before half the active nuclei decays.<\/p>\n\n\n\n Let the initial number of the active nuclei present in the sample be N<\/em>0<\/sub>.<\/p>\n\n\n\n No2=Noe-\u03bbt12\u21d2t12=ln 2\u03bbAverage life of the nuclei,<\/p>\n\n\n\n tav=SNo=1\u03bbHere, S<\/em> is the sum of all the lives of all the N<\/em> nuclei that were active at t<\/em> = 0 and<\/p>\n\n\n\n \u03bb is the decay constant of the sample.<\/p>\n\n\n\n An \u03b1-particle is bombarded on 14<\/sup>N. As a result, a 17<\/sup>O nucleus is formed and a particle is emitted. This particle is a (b) proton<\/p>\n\n\n\n If an alpha particle is bombarded on a nitrogen (N-14) nucleus, an oxygen (O-17) nucleus and a proton are released. H24e+N714\u2192O617+p11So, the emitted particle is a proton.<\/p>\n\n\n\n Ten grams of 57<\/sup>Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly (a) 10 g<\/p>\n\n\n\n 57<\/sup>Co is undergoing beta decay, i.e. electron is being produced. But an electron has very less mass (9.11<\/p>\n\n\n\n \u00d710-31 <\/sup>kg) as compared to the Co atom. Therefore, after 570 days, even though the atoms undergo large beta decay, the weight of the material in the container will be nearly 10 g.<\/p>\n\n\n\n Free 238<\/sup>U nuclei kept in a train emit alpha particles. When the train is stationary and a uranium nucleus decays, a passenger measures that the separation between the alpha particle and the recoiling nucleus becomes x<\/em> in time t<\/em> after the decay. If a decay takes place when the train is moving at a uniform speed v<\/em>, the distance between the alpha particle and the recoiling nucleus at a time t<\/em> after the decay, as measured by the passenger will be (c) x<\/em><\/p>\n\n\n\n When the train is stationary, the separation between the alpha particle and recoiling uranium nucleus is x<\/em> in time t<\/em> after the decay. Even if the decay is taking place in a moving train and the separation is measured by the passenger sitting in it, the separation between the alpha particle and nucleus will be x<\/em>. This is because the observer is also moving with the same speed with which the alpha particle and recoiling nucleus are moving, i.e. they all are in the same frame that is moving at a uniform speed.<\/p>\n\n\n\n During a nuclear fission reaction, (c) a heavy nucleus bombarded by thermal neutrons breaks up<\/p>\n\n\n\n In a nuclear reactor, a large fissile atomic nucleus like uranium-235 absorbs a thermal neutron and undergoes a nuclear fission reaction. The heavy nucleus splits into two or more lighter nuclei releasing gamma radiation and free neutrons.<\/p>\n\n\n\n As the mass number A<\/em> increases, which of the following quantities related to a nucleus do not change? (c) Density<\/p>\n\n\n\n Radius of a nucleus with mass number A<\/em> is given as 4\u03c0R33=4\u03c0Ro3A3<\/p>\n\n\n\n This depends on A. <\/em>With an increase in A,V<\/em> increases proportionally. \u2243 AmN<\/sub><\/em> On the other hand, MassVolume=AmN4\u03c0R33=AmN4\u03c0Ro3A3=mN4\u03c0Ro33=3mN4\u03c0Ro3This is independent of A<\/em> and hence does not change as mass number increases.<\/p>\n\n\n\n The heavier nuclei tend to have larger N\/Z<\/em> ratio because (c) a neutron does not exert electric repulsion This is because in heavy nuclei, the N\/Z<\/em> ratio becomes larger in order to maintain their stability and reduce instability caused due to the repulsion among the protons.The neutrons exert only attractive short-range nuclear forces on each other as well as on the neighbouring protons, whereas the protons exert attractive short-range nuclear forces on each other as well as the electrostatic repulsive force. Thus, the nuclei with high mass number, in order to be stable, have large neutron to proton ratio (N\/Z<\/em>).<\/p>\n\n\n\n A free neutron decays to a proton but a free proton does not decay to a neutron. This is because (c) neutron has large rest mass than the proton.<\/p>\n\n\n\n A nucleus is made up of two fundamental particles- neutrons and protons. If a nucleus has more number of neutrons than what is needed to have stability, then neutrons decay into protons and if there\u2019s an excess of protons, then they decay to form neutrons. Since a neutron has larger rest mass than a proton, the Q<\/em>-value of its decay reaction is positive and a free neutron decays to a proton, while an isolated proton cannot decay to a neutron as the Q<\/em>-value of its decay reaction is negative. Hence, it is physically not possible.<\/p>\n\n\n\n Consider a sample of a pure beta-active material. (d) The active nucleus changes to one of its isobars after the beta decay.<\/p>\n\n\n\n In a beta decay, either a neutron is converted to a proton or a proton is converted to a neutron such that the mass number does not change. Also,the number of the nucleons present in the nucleus remains the same. Thus, the active nucleus gets converted to one of its isobars after beta decay.<\/p>\n\n\n\n In which of the following decays the element does not change? (d) \u03b3-decay<\/p>\n\n\n\n \u00e2\u20ac\u2039In alpha particle decay, the unstable nucleus emits an alpha particle reducing its proton number Z<\/em> by 4 and neutron number N<\/em> by 2 such that the element gets changed. XZA\u2192YZ-2A-4+H24e XZA\u2192YZ+1A+e+\u03bd\u00af XZA\u2192YZ-1A+\u03b2++\u03bd In which of the following decays the atomic number decreases? (a) \u03b1-decay \u00e2\u20ac\u2039In alpha particle decay, the unstable nucleus emits an alpha particle reducing its proton number (atomic number) Z<\/em> as well as neutron number N<\/em> by 2. XZA\u2192YZ-2A-4+H24e XZA\u2192YZ+1A+e-+\u03bd\u00af XZA\u2192YZ-1A+\u03b2++\u03bd Magnetic field does not cause deflection in (d) gamma rays<\/p>\n\n\n\n Magnetic force acts on a charged particle, due to which it deflects from its path. The magnitude of this force is measured as<\/p>\n\n\n\n F\u2192=q(v\u2192\u00d7B\u2192).Answer:<\/h4>\n\n\n\n
Question 6:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Question 7:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Binding energy = [(Number of nucleons)<\/p>\n\n\n\n
E = <\/em>\u0394mc<\/em>2<\/sup><\/p>\n\n\n\nQuestion 8:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Question 9:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
According to the charge and mass conservation,<\/p>\n\n\n\nQuestion 10:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Question 11:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Hence the correct option is D.<\/p>\n\n\n\nQuestion 12:<\/h4>\n\n\n\n
Answer:<\/h4>\n\n\n\n
Question 1:<\/h4>\n\n\n\n
(a) exact 12 u
(b) less than 12 u
(c) more than 12 u
(d) depends on the form of carbon such as graphite of charcoal.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 2:<\/h4>\n\n\n\n
(a) the number of neutrons in the nucleus
(b) the number of protons in the nucleus
(c) the number of nucleons in the nucleus
(d) none of them.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 3:<\/h4>\n\n\n\n
(a) two extra protons and two extra electrons
(b) two extra protons but no extra electrons
(c) two extra neutrons and no extra electron
(d) two extra neutrons and two extra electron.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 4:<\/h4>\n\n\n\n
(a) always less than its atomic number
(b) always more than its atomic number
(c) equal to its atomic number
(d) sometimes more than and sometimes equal to its atomic number.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 5:<\/h4>\n\n\n\n
(a) a straight line
(b) a parabola
(c) an ellipse
(d) none of them.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
The average nuclear radius (R<\/em>) and the mass number of the element (A<\/em>) has the following relation:<\/p>\n\n\n\nQuestion 6:<\/h4>\n\n\n\n
(a) Fpp<\/sub><\/em> > Fpn<\/sub><\/em> = Fnn<\/sub><\/em>
(b) Fpp<\/sub><\/em> = Fpn<\/sub><\/em> = Fnn<\/sub><\/em>
(c) Fpp<\/sub><\/em> > Fpn<\/sub><\/em> > Fnn<\/sub><\/em>
(d) Fpp<\/sub><\/em> < Fpn<\/sub><\/em> = Fnn<\/sub><\/em><\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 7:<\/h4>\n\n\n\n
(a) Fpp<\/sub><\/em> > Fpn<\/sub><\/em> = Fnn<\/sub><\/em>
(b) Fpp<\/sub><\/em> = Fpn<\/sub><\/em> = Fnn<\/sub><\/em>
(c) Fpp<\/sub><\/em> > Fpn<\/sub><\/em> > Fnn<\/sub><\/em>
(d) Fpp<\/sub><\/em> < Fpn<\/sub><\/em> = Fnn<\/sub><\/em><\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Here, F<\/em>pp<\/sub>, F<\/em>pn<\/sub> and F<\/em>nn<\/sub> denote the magnitudes of the nuclear force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron, respectively.<\/p>\n\n\n\nQuestion 8:<\/h4>\n\n\n\n
(a) Fe<\/sub><\/em> = Fn<\/sub><\/em>
(b) Fe<\/sub><\/em> >> Fn<\/sub><\/em>
(c) Fe<\/sub><\/em> << Fn<\/sub><\/em>
(d) Fe<\/sub><\/em> and Fn<\/sub><\/em> differ only slightly.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Page No 441:<\/h4>\n\n\n\n
Question 9:<\/h4>\n\n\n\n
(a) increases
(b) decreases
(c) remains the same
(d) varies in a way that depends on the actual value of A<\/em>.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 10:<\/h4>\n\n\n\n
(a) It is the energy required to break a nucleus into its constituent nucleons.
(b) It is the energy made available when free nucleons combine to form a nucleus.
(c) It is the sum of the rest mass energies of its nucleons minus the rest mass energy of the nucleus.
(d) It is the sum of the kinetic energy of all the nucleons in the nucleus.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 11:<\/h4>\n\n\n\n
(a) half the active nuclei decay
(b) less than half the active nuclei decay
(c) more than half the active nuclei decay
(d) all the nuclei decay.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
It is given as<\/p>\n\n\n\nQuestion 12:<\/h4>\n\n\n\n
(a) Proton
(b) Neutron
(c) Electron
(d) Photon<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 13:<\/h4>\n\n\n\n
(a) an atomic electron is ejected
(b) an electron which is already present within the nucleus is ejected
(c) a neutron in the nucleus decays emitting an electron
(d) a proton in the nucleus decays emitting an electron.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Neutron decays to produce proton, electron and anti-neutrino.<\/p>\n\n\n\nQuestion 14:<\/h4>\n\n\n\n
(a) 6 h
(b) 12 h
(c) 24 h
(d) 128 h.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 15:<\/h4>\n\n\n\n
(a) 1\/\u03bb and (In 2\/\u03bb)
(b) (In 2\/\u03bb) and 1\/\u03bb
(c) \u03bb(In 2) and 1\/\u03bb
(d) \u03bb\/(In 2) and 1\/\u03bb.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 16:<\/h4>\n\n\n\n
(a) neutron
(b) proton
(c) electron
(d) positron.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
According to the conservation of mass and charge,<\/p>\n\n\n\nQuestion 17:<\/h4>\n\n\n\n
(a) 10 g
(b) 5 g
(c) 2.5 g
(d) 1.25 g.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 18:<\/h4>\n\n\n\n
(a) x<\/em> + vt<\/em>
(b) x<\/em> \u2212 vt<\/em>
(c) x<\/em>
(d) depends on the direction of the train.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 19:<\/h4>\n\n\n\n
(a) a heavy nucleus breaks into two fragments by itself a light nucleus bombarded by thermal neutrons breaks up
(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 possible other products.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 1:<\/h4>\n\n\n\n
(a) Mass
(b) Volume
(c) Density
(d) Binding energy<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
R=RoA13
Here, Ro<\/sub><\/em> = 1.2 fm
\u2234 Volume of the nucleus =<\/p>\n\n\n\n
Mass of the nucleus<\/p>\n\n\n\n
Here, mN<\/sub><\/em>is the mass of a nucleon.
Therefore, mass of the nucleus also increases with the increasing mass number.
Binding energy also depends on mass number (number of nucleons) as it is the difference between the total mass of the constituent nucleons and the nucleus. Therefore, it also varies with the changing mass number.<\/p>\n\n\n\n
Density =<\/p>\n\n\n\nQuestion 2:<\/h4>\n\n\n\n
(a) a neutron is heavier than a proton
(b) a neutron is an unstable particle
(c) a neutron does not exert electric repulsion
(d) Coulomb forces have longer range compared to the nuclear forces.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
(d) Coulomb forces have longer range compared to the nuclear forces<\/p>\n\n\n\nQuestion 3:<\/h4>\n\n\n\n
(a) neutron is a composite particle made of a proton and an electron whereas proton is a fundamental particle
(b) neutron is an uncharged particle whereas proton is a charged particle
(c) neutron has large rest mass than the proton
(d) weak forces can operate in a neutron but not in a proton.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 4:<\/h4>\n\n\n\n
(a) All the beta particles emitted have the same energy.
(b) The beta particles originally exist inside the nucleus and are ejected at the time of beta decay.
(c) The antineutrino emitted in a beta decay has zero mass and hence zero momentum.
(d) The active nucleus changes to one of its isobars after the beta decay.<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Question 5:<\/h4>\n\n\n\n
(a) \u03b1-decay
(b) \u03b2+<\/sup>-decay
(c) \u03b2\u2212<\/sup>-decay
(d) \u03b3-decay<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
<\/p>\n\n\n\n
During \u03b2\u2212<\/sup>-decay\u00e2\u20ac\u2039, a neutron is converted to a proton\u00e2\u20ac\u2039, an electron and an antineutrino, i.e. an active nucleus gets converted to one of its isobars and hence the element gets changed.<\/p>\n\n\n\n
During \u03b2+<\/sup>\u2013decay\u00e2\u20ac\u2039, a proton in the nucleus is converted to a neutron\u00e2\u20ac\u2039, a positron and a neutrino in order to maintain the stability of the nucleus, i.e. an active nucleus gets converted to one of its isobars and hence the element gets changed.<\/p>\n\n\n\n
When a nucleus is in higher excited state or has excess of energy, it comes to the ground state in order to become stable and release energy in the form of electromagnetic radiation called gamma ray. Hence, the element in gamma decay doesn\u2019t change.<\/p>\n\n\n\nQuestion 6:<\/h4>\n\n\n\n
(a) \u03b1-decay
(b) \u03b2+<\/sup>-decay
(c) \u03b2\u2212<\/sup>-decay
(d) \u03b3-decay<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
(b) \u03b2+<\/sup>-decay<\/p>\n\n\n\n
<\/p>\n\n\n\n
During \u03b2\u2212<\/sup>-decay\u00e2\u20ac\u2039, a neutron is converted to a proton\u00e2\u20ac\u2039, an electron and an antineutrino. Thus, there is an increase in the atomic number.<\/p>\n\n\n\n
During \u03b2+<\/sup>-decay\u00e2\u20ac\u2039, a proton in the nucleus is converted to a neutron\u00e2\u20ac\u2039, a positron and a neutrino in order to maintain the stability of the nucleus. Thus, there is a decrease in the atomic number. \u00e2\u20ac\u2039<\/p>\n\n\n\n
When a nucleus is in higher excited state or has excess of energy, it comes to the lower state in order to become stable and release energy in the form of electromagnetic radiation called gamma ray. The element in the gamma decay doesn\u2019t change.
Therefore, alpha and beta plus decay suffer decrease in atomic number.<\/p>\n\n\n\nQuestion 7:<\/h4>\n\n\n\n
(a) \u03b1-rays
(b) beta-plus rays
(c) beta-minus rays
(d) gamma rays<\/p>\n\n\n\nAnswer:<\/h4>\n\n\n\n
Here, q <\/em>is the charge on the particle that is moving with speed