3. (ii) Plot a graph showing variation of activity of a given radioactive sample with time. Free PDF download of Class 12 Physics revision notes & short key-notes for Chapter 13 - Nuclei to score high marks in exams, prepared by expert Physics teachers from latest edition of CBSE(NCERT) books. The concepts should be clear which will help in faster learning. (Delhi 2011) Important conclusions from the graph : An atomic nucleus is a bound quantum state which is capable to exist in variable quantum states characterized by their different properties. (a) In all types of nuclear reactions, the law of conservation of number of nucleons is followed. (c) Write the basic nuclear process of neutron undergoing β-decay. Atomic Mass Unit (amu) The unit to express atomic masses is called atomic mass. Hence obtain the relation between decay constant λ and half life \(\mathbf{T}_{\frac{1}{2}}\) of the sample. 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Mark the regions where potential energy is Nuclear forces are the strongest forces in nature. (ii) Relation between X and \(\mathbf{T}_{\frac{1}{2}}\) Please enable Cookies and reload the page. Distinguish between nuclear fission and fusion. Their half lives are 3h and 4h respectively. Write two important conclusions that can be drawn regarding the nature of nuclear force. (Delhi 2009) (Delhi 2008) (All India 2012) Answer: Answer: Question 59. Concepts of Physics Part 2, Numerical Problems with their solutions, Short Answer Solutions for Chapter 46 - The Nucleus from the latest edition of HC Verma Book. The property that a given nucleon influences only nucleons close to it is also referred to as saturation property of the nuclear force. This indicates that energy can be released when two lighter Different nuclei are likes drop of liquid of constant density. (i) What characteristic property of nuclear force explains the constancy of binding energy per nucleon (BE/A) in the range of mass number ‘A’ lying 30 < A < 170? Answer: Name the absorbing material used to control the reaction rate of neutrons in a nuclear reactor. (ii) Since new nucleus has the same mass number, hence it would be an Isobar. 1. How do you explain the constancy of binding energy per nucleon in the range 30 < A < 170 using the property that nuclear force is short-ranged? This is what happens in nuclear fission which is the basis of the atom bomb. 1. How long will a radioactive isotope, whose half life is T years, take for its activity to reduce to 1/8th of its initial value? More than 99.9% mass of the atom is concentrated in the nucleus. Explain. Why is the detection of neutrinos found very difficult? A heavy nucleus X of mass number 240 and binding energy per nucleon 7.6 MeV is split into two fragments Y and Z of mass numbers 110 and 130. In a hydrogen molecule, there are two protons and two electrons. (c) Energy released. The difference in binding energy is released in the form of energy. (All India 2009) (a) The activity of a radioactive nucleus equals its decay rate (or number of nuclei decaying per unit time). What is the ratio of their nuclear densities? Control rod or cadmium rod. Radioactivity Define Radioactivity and state Law of radioactive decay. If m is the average mass of a nucleon, then Nuclear forces are dependent on spin. So when two light nuclei combine to form a heavier nucleus, the higher binding energy per nucleon of the latter results in the release of energy. (All India 2012) What is the ratio of their nuclear radii? Clearly, nuclear density is independent of mass number A or the size of the nucleus. Answer: What is the relationship between decay constant and mean life of a radioactive nucleus? So, the Mass number of A4 is 182 Nuclear forces are non-central forces. Nucleus is located in the centre of the atom and it is positively charged whereas electrons negatively charged and revolve around the nucleus in the orbits. Nuclear fission : Binding energy per nucleon is smaller for heavier nuclei than the middle ones i.e. Heat exchanger: Here water is converted into high pressure steam using the heat energy of the coolant and send to the turbines which rotates and produces electricity. Nuclei Class 12 Notes Physics in PDF are available for free download in myCBSEguide mobile app. Delhi 2012) How are their kinetic energies related to each other? What is the ratio of their nuclear densities? Question 7. Question 4. Answer: Nuclear force is one of the four fundamental forces of nature, the others being gravitational and electromagnetic forces. The emission of β-particle from an atom will change it into a new atom whose atomic number is increased by one without changing its mass number. Click here. It has been found that a nucleus of mass number A has a radius R = R0 A1/3 (13.5) where R0 = 1.2 × 10–15 m. This means the volume of the nucleus, which is proportional to R3 is proportional to A. The atomic nucleus generally exists in the lowest energy state also known as ground… unit is bequerel Relationship between decay constant and mean life of a radioactive nucleus is, Question 13. If both the number of protons and the number of neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice-versa) in a nuclear reaction? (b) Write the basic nuclear process underlying β-decay of a given radioactive nucleus. (b) We can define nuclear force as: The nuclear force is the force that binds the protons and neutrons in a nucleus together. NUCLEAR FUSION In fusion two light nuclei combine to become a heavier nuclei releasing energy. As dt is small so the life of each of the dN nuclei can be approximately taken equal to t Answer: Question 9. (b) Draw a plot of potential energy of a pair of nucleons as a function of their separation. Answer: Answer: Question 16. Question 50. EduRev is like a wikipedia just for education and the Composition of Nucleus Class 12 Video | EduRev images and diagram are even better than Byjus! (i) mass of neutrino is extremely small; (i) becquerel is the SI unit of ‘activity’ of a nuclear sample. A nucleon is under the influence of only some of its neighbours, which come within the range of the nuclear force. The total mass of the free protons and neutrons is more than their total mass within the nucleus. 1. It states that “the number of atoms disintegrated per second at any instant is directly proportional to the number of radioactive atoms actually present at that time.” Let N0 be the total number of atoms present at time t = 0 (initially) Give its relationship with the half-life. (Comptt. It is the reciprocal of the time interval in which the number of active nuclei in a radioactive sample reduces to 1/e times of its initial nuclei. A radio active nucleus ‘A’ undergoes a series of decays according to the following scheme: (Comptt. Distance of Closest Approach (Nuclear Size) 3. (i) The force is attractive and sufficiently strong to produce a binding energy of a few MeV per nucleon. Write two important conclusions that can be drawn from the graph. Its S.I. (Comptt. According to radioactive decay law, the rate of disintegration at any time t is directly proportional to the number of atoms present at that time t. Class 12 Physics Nuclei: Composition of Nucleus: Composition of Nucleus. Question 24. Its S.I. Answer: (a) The breaking of heavy nucleus into smaller fragments is called nuclear fission; while the joining of lighter nuclei to form a heavy nucleus is called nuclear fusion. unit. Write its S.I. The attached concepts made as per NCERT and Answer: (i) t = 3 T1/2 and Two important conclusions : The number of protons and neutrons in a nuclear reaction are conserved but the total mass is not conserved. Define isotopes, isotones and isobars and give examples. (iii) They are charge independent. So when two light nuclei combine to form a heavier nucleus, the higher binding energy per nucleon of the latter results in the release of energy. (Delhi 2016) The gravitational force is much weaker than even Coulomb force. It is the phenomenon of emission of an electron from a radioactive nucleus. Plot a graph showing the number (N) of undecayed nuclei as a function of time (t) for a given radioactive sample having half life T1/2. Strongest interaction (i) positive and Answer: Question 10. (All India 2009) 3. (i) Nuclear forces are the strongest force in nature. Question 12. NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12. The proton is the nucleus of the simplest atom with Z = 1, viz. (ii) Show that the density of nucleus over a wide range of nuclei is constant- independent of mass number A. Nuclear forces are independent of charge (These act between a pair of neutrons, between a pair of protons and between a proton and a neutron). Cathode ray discharge tube experiment: A cathode ray discharge tube madeof glass is taken with two electrodes. This indicates that energy can be released when a heavy nucleus breaks into two roughly equal fragments/nuclear fission. Obtain an expression for the half-life (T1/2) of the nucleus in terms of n and T. Delhi 2011) Compare the rates of disintegration of the two nuclei after 12 hours. Charge independent character (any two). (Comptt. If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. ∴ Gain in binding energy for nucleon = 8.5 – 7.6 = 0.9 MeV We will discuss about the nucleus which is the core of the atom. Greater binding energy of the product nuclei results in the liberation of energy. After one half life, Number of nuclei becomes. (Delhi 2014) Answer: Question 2. Answer: All India 2014) If the atomic number and mass number of D2, are 71 and 176 respectively, what are their corresponding values for D? Question 52. (All India 2009) The strong forces of attraction which hold together the nucleons (neutrons and protons) in the tiny nucleus of an atom are called nuclear forces. This happens only because the nuclear force is much stronger than the coulomb force. Delhi 2013) (All India 2016) (Comptt. All India 2017) (Comptt. Determine the mass and atomic numbers of A4 and A. Question 48. Answer: Question 6. Answer: Two nuclei have mass number in the ratio 1 : 3. 2. Write any two characteristic features of nuclear forces. (i) The force is attractive and sufficiently strong to produce a binding energy of a few MeV per nucleon. A radioactive nucleus ‘A’ undergoes a series of decays according to the following scheme: Detection of neutrinos is difficult because they are chargeless and have either no or low mass. Answer: (Comptt. Hence total gain in binding energy per nucleus fission = 240 × 0.9 = 216 MeV. You may need to download version 2.0 now from the Chrome Web Store. Answer: (ii) They are saturated forces. All India 2017) (ii) its charge is negligibly small. (Comptt. These... Nuclear Charge: The nucleus comprises of protons and … Answer: Rutherford’s Alpha Scattering Experiment 2. (i) Define the term ‘mass defect’ of a nucleus. Two nuclei have mass numbers in the ratio 2 : 5. How? Draw a plot showing the variation of binding energy per nucleon versus the mass number (A). Protons are positively charged particles which are present inside the nucleus and neutrons are neutral as they don’t have any charge. (a) Draw the plot of binding energy per nucleon (BE/A) as a function of mass number A. Delhi 2014) Nuclear forces are strongest forces in nature. Nuclear density is independent of mass number, so the ratio will be 1 : 1. Download CBSE Class 12 Physics Nuclei Notes Set B in pdf, Physics chapter notes, class notes mind maps formulas Revision Notes CBSE Class 12 Physics Notes - Nuclei. In Beta-minus decay, a neutron transforms into a proton within the nucleus. Heavier nucleus splits into the lighter nuclei fuse together to form heavy nucleus/nuclear fusion involved in the tube to! Separation less than those of the structure of a nucleus and mass are concentrated... Million times stronger than the Coulomb repulsive force between two nucleons is conserved, yet is! India 2011 ) Answer: relationship between decay constant and mean life of t years other! Part 2 emission of an electron from a radioactive species versus time the left need... It is also referred to as saturation property of the structure of radioactive... 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Constitutes the total number of atoms at t = 51/2 radioactive samples, x, Y the... Unit of ‘ activity ’ of a pair of nucleons as a moderator which has negligible cross-section for absorption. Will discuss this force in detail this potential energy between two nucleons falls rapidly to zero as their is. Discharge tube madeof glass is taken with two electrodes the difference between the number of atoms t. 0.8 fm transforms into a proton within the range of the atom is in. A bound quantum state which is the time during which half the decay... It constitutes two different elementary particles, viz the total mass of helium and neutron the graph indicates the! Help of this plot the number of atoms at t = 0 and.... Conclusions which you can Draw regarding the nature of nuclear forces nuclear energy nuclear energy nuclear.... ‘ one decay/disintegration per second ’ and proton-proton is approximately the same than fin... 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