NUCLEAR PHYSICS PREVIOUS EAMCET BITS ENGINEERING 0.693

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Alvin Day
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1 - NUCLE PHYSICS PEVIOUS EMCET BITS ENGINEEING. The radioactivity of a sample is X at a time tbb and Y at a time tbb. If the mean life time of the specimen is τ, the number of atoms that have disintegrated in the time interval (t B B- tbb) is : Xt ) Yt ) X-Y ) X Y τ ns : 4 The relation between t /.9 and is t / tbb X () tbb Y.() from () and () X Y (tb B t BB) X Y t t but τ 4) ( X ) Y τ (9 E) tbb tbb (X Y) τ. Let F pp,f pn and F nn 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 less than one fermi, then (8 E) ) F pp >F pn F nn ) F pp F pn F nn ) F pp >F pn >F nn 4) F pp <F pn F nn ns: Sol. Nuclear forces are charge independent. In sun, the important source of energy is (E-7) ) proton-proton cycle ) carbon-nirtogen cycle ) carbon-caron cycle 4) nitrogen-nitrogen cycle ns: Sol. Because of nuclear fusion proton proton cycle takes place 4. free neutron decays spontaneously into: [E] ) a proton, an electron and an anti-neutrino ) a proton, an electron and a neutrino ) a proton and electron 4) a proton, an electron, a neutrino and an anti-neutrino ns: Sol. n o e Particles and their anti-particles have: [5E] ) the same masses but opposite spins ) the same masses but opposite magnetic moments. ) the same masses and same magnetic moments

2 4) opposite spins and same magnetic moments ns: Sol. Same masses but opposite electromagnetic properties like charge, magnetic moment etc.. Consider the following two statements and B and identify the correct answer given below: : Nuclear density is same for all nuclei [4 E] B: adius of the nucleus () and its mass number () are related as / ) Both and B are true ) Both and B are false ) is true and B is false 4) is false B is true ns : Density remains constant ( ): ρ constant (B) : (B) / / sin ce / 7. The mass defect in a particular nuclear reaction is.grams. The amount of energy liberated in kilowatt hours is : (Cx 8 m/s) [E] 5 ) 7.5 KWH ) ns: 4 From Einstein mass energy equivalence E MC ( ). 8.7 J KWH ) 7.5 KWH 4) 7.5 KWH 7.75 P P KWH 7.5 KWH 8. Consider the following statements and B. Identify the correct choice in the given answer. () p-p, p-n, n-n forces between nucleons are not equal and charge dependent (B) In nuclear reactor the fission reaction will be in accelerating state if the value of neutron reproduction factor k > ( E) ) Both and B are correct ) Both an d B are wrong ) is wrong and B is correct 4) is correct and B is wrong. ns : : The p-n, p-p and n-n nuclear forces are equal and charge independent. Neutronsinone generation B : K Neutron sin the previous generation Where k is called neutron multiplication factor If K >, the neutron population keeps on increasing after the completion of each neutron cycle which takes time of the order of a millisecond. Which is called as super critical state 9. True masses of neutron, proton and deutron in a.m.u are.89,.8 and.47 respectively. The packing fraction of the deutron in a.m.u is ( E) ).5 x 4 ).5 x -4

3 ) 7. x 4 4) 47.5 x 4 ns : Packing fraction M, where M is the atomic mass and is the mass number. M.47 4 P 7.. heavy nucleus at rest breaks into two fragments which fly off with velocities 8:. The ratio of radii of fragments is ( E) ) :) :4 ) 4: 4) : ns: Sol Momentum conservation gives mv mv v 8 m v m m m 8 / / 8 MEDICL. tomic mass of C is.5 amu and its mass number is.. If amu9 MeV, binding energy of the neutrons present in the nucleus is: (9 M) ).4 MeV ).44 MeV ).8 MeV 4). MeV ns: Mass defect.5 amu binding energy of neutrons (.5)( 9) MeV. The following particles are Baryons: (8 M) ) Nucleons and hyperons ) Nucleons and leptons ) Hyperons and leptons 4) Hyperons and Bosons ns: Sol. Nucleons and hyperons are called Baryons. Electron belongs to the following class of elementary particles [7M] ) Hardon ) Lepton ) Boson 4) Baryon ns: Sol. s electrons have lighter mass. Therefore they belong to leptons 4. ssertion(): Nuclear forces arise from strong Coulombic interactions between protons and neutrons. eason (): Nuclear forces are independent of the charge of the nucleons. [M] ) Both and are true and is the correct explanation of

4 and are ) Both and are true but is the not correct explanation of ) is true, but is false 4) is false, but is true ns: 4 5 The particle that possesses half integral spin is: [5M] ) Photon ) Pion ) Proton 4) K-meson ns: Sol. Proton Possesses half integral spin. Matching pairs in the two lists given below are [4M] List-I List-II ) Gravitions E) Hyperons B) Baryons F) Positrons C) Pions G) Particles with zero mass and with a spin of unity D) Leptons H) Decay to -mesons I) Massless particles with a probable spin of two units. ) -E,B-H,C-G,D-I ) -I,B-E,C-H,D-F ) -H,B-F,C-I,D-E 4) -F,B-G,C-E,D-H ns: 7. nucleus splits into two nuclear parts having radii in the ratio :. Their velocities are in the ratio [M] ) 8: ) : ) 4: 4) : ns: / M [ since mass volume x density ] M 8 M V M V [ from law of conservation of momentum ] V M V M 8 8. : Density of nucleus is independent of its mass number B: Beryllium is used as a moderator in nuclear reactors ( M) ) Both and B are correct ) Both and B are wrong ) is correct,b is wrong 4) is wrong,b is correct ns : mass of nucleus M p : ρ volume 4 π / M p M p 4π / r 4π r constant [ since mbpb rbb constant] ( ) B: good moderator must be light (low atomic weight) must be capable of scattering neutrons with a high probability, but should not absorb neutrons. Therefore Beryllium is not suitable for moderator 9. In Carbon-Nitrogen fusion cycle, protons are fused to form a helium nucleus, positrons and release some energy. The number of protons fused and the number of positrons released in this process respectively are ( M) 4

5 ) 4,4 ) 4, ),4 4) 4, ns : 4 H He + e + γ 4 4 protons fuses and positron are released. The ratio of radii of nuclei l 7 and 5 Te 5 is ( M) ) : 5 ) : 5 ) 4 : 5 4) : 5 ns:4 / r / / In a nuclear reactor using U 5 as a fuel, the power output is 4.8MW. The number of fissions per second is ( M) (Energy released per fission MeV, ev.x -9 J) ).5x 7 ) x 9 ).5x 5 4) x 5 ns : Power of reactor P ne t Where n is number of fissions, t is time and E is energy released per fission 5

MockTime.com. Ans: (b) Q6. Curie is a unit of [1989] (a) energy of gamma-rays (b) half-life (c) radioactivity (d) intensity of gamma-rays Ans: (c)

MockTime.com. Ans: (b) Q6. Curie is a unit of [1989] (a) energy of gamma-rays (b) half-life (c) radioactivity (d) intensity of gamma-rays Ans: (c) Chapter Nuclei Q1. A radioactive sample with a half life of 1 month has the label: Activity = 2 micro curies on 1 8 1991. What would be its activity two months earlier? [1988] 1.0 micro curie 0.5 micro