Nuclei PYQs Set 3 (PDF)

Set 3 of 8 · Questions 61-90 of 237

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Mere Teacher · Previous Year Questions NEET Physics · Nuclei · Set 3 (Q61-90)
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61. $A radioactive nucleus decays by two different processes. The halflife for the first process is 10 s and that for the second is 100 s . The effective half life of the nucleus is close to$ (1) $12 sec$ (2) $9 sec$ (3) $55 sec$ (4) $6 sec$ 62. $Which of the following is emitted, when_{94}^{239} Pu decays into_{92}^{235} U ?$ (1) $Gamma ray$ (2) $Neutron$ (3) $Electron$ (4) $Alpha particle$ 63. $The radius and mass number of nucleus ' 1 ' is R_{1} and A_{1} respectively. The radius and mass number of nurleus ' 2 ' is R_{2} and A_{2} respectively. If A_{2} is larger than A_{1} by 2 %, then R_{2} is larger than R_{1} by$ (1) $\frac{2}{3} %$ (2) $1 %$ (3) $8 %$ (4) $\frac{3}{2} %$ 64. $The half-life of Au^{198} is 2.7 days. The activity of 1.50 mg of Au^{198} if its atomic weight is 198 g mol^{- 1} is, (N_{A} = 6 \times 10^{23} / mol)$ (1) $240 Ci$ (2) $357 Ci$ (3) $535 Ci$ (4) $252 Ci$ 65. $A radioisotope X with a halflife 1.4 \times 1 0^{9} years decays to Y which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1 : 7. The age of the rock is$ (1) $1.96 \times 1 0^{9} years$ (2) $3.92 \times 1 0^{9} years$ (3) $4.20 \times 1 0^{9} years$ (4) $8.40 \times 1 0^{9} years$ 66. $The mass of a_{3}^{7} Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of_{3}^{7} Li nucleus is nearly$ (1) $46 MeV$ (2) $5.6 MeV$ (3) $3.9 MeV$ (4) $23 MeV$ 67. $The masses of two radioactive substances are same and their half lives are 1 year and 2 years respectively. The ratio of their activities after 6 years will be$ (1) $1 : 3$ (2) $1 : 6$ (3) $1 : 4$ (4) $1 : 2$ 68. $A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u . The energy liberated per u is (given 1 u = 931 MeV)$ (1) $6.675 MeV$ (2) $13.35 MeV$ (3) $2.67 MeV$ (4) $26.7 MeV$ 69. $The energy equivalent to a mass of 1 kg is$ (1) $9 \times 10^{13} J$ (2) $9 \times 10^{9} J$ (3) $9 \times 10^{16} J$ (4) $9 \times 10^{6} J$ 70. $The half life of a radioactive substance is 20 minutes. The time taken between 50 % decay and 87.5 % decay of the substance will be$ (1) $40 minutes$ (2) $10 minutes$ (3) $30 minutes$ (4) $25 minutes$ 71. $The radius of the first permitted Bohr orbit, for the electron, in a hydrogen atom equals 0.51Å and its ground state energy equals -13.6 eV. If the electron in the hydrogen atom is replaced by muon (μ^{-}) [charge same as electron and mass 207 m_{e}], the first Bohr radius and ground state energy will be$ (1) $0.53 \times 10^{- 13} m, - 3.6 eV$ (2) $25.6 \times 10^{- 13} m, - 2.8 eV$ (3) $2.56 \times 10^{- 13} m, - 2.8 keV$ (4) $2.56 \times 10^{- 13} m, - 13.6 eV$ 72. $In a nuclear reactor, the main purpose of the moderator is to$ (1) $initiate that fission process by giving away its neutron$ (2) $slow down the fast neutrons$ (3) $cool down the excess of heat generated in the reactor$ (4) $absorb excess of neutrons and control the reaction rate$ 73. $A nucleus of mass M emits γ -ray photon of frequency 'v' The loss of internal energy by the nucleus is: [Take 'c' as the speed of electromagnetic wave]$ (1) $hc$ (2) $0$ (3) $hv (1 - \frac{hv}{2 M c ^{2}})$ (4) $hv (1 + \frac{hv}{2 M c ^{2}})$ 74. $The particles emitted in the decay of_{92}^{238} U to_{92}^{234} U$ (1) $2 α and 2β$ (2) $1 α and 2 β$ (3) $1α and 1 β$ (4) $1 α only$ 75. $The half life of radium is about 1600 years. If 100 g of radium existing now, 25 g will remain unchanged after$ (1) $4800 years$ (2) $6400 years$ (3) $2400 years$ (4) $3200 years$ 76. $A nuclear reactor delivers a power of 10^{9} W, the amount of fuel consumed by the reactor in one hour is$ (1) $0.72 g$ (2) $0.04 g$ (3) $0.96 g$ (4) $0.08 g$ 77. $The ratio of magnetic dipole moment of an electron of charge c and mass m in Bohr's orbit in hydrogen atom to its angular momentum is$ (1) $\frac{e}{m}$ (2) $\frac{m}{e}$ (3) $\frac{2 m}{e}$ (4) $\frac{c}{2 m}$ 78. $On bombarding U^{235} by slow neutron, 200 MeV energy is released. If the power output of atomic reactor is 1.6 MW, then the rate of fission will be$ (1) $8 \times 10^{16} / s$ (2) $20 \times 10^{16} / s$ (3) $5 \times 10^{22} / s$ (4) $5 \times 10^{16} / s$ 79. $An element A decays into element C by a two step process A \to B +_{2} He^{4}; B \to C + 2 e^{-}, Then$ (1) $A and C are isotopes$ (2) $A and C are isobars$ (3) $A and B are isotopes$ (4) $A and B are isobars$ 80. $The half-life of_{84}^{209} P_{0} is 103 years. The time it takes fc 100 g sample of_{84}^{209} P_{0} to decay to 3.125 g is$ (1) $3296 years$ (2) $1032 years$ (3) $1648 years$ (4) $515 years$ 81. $A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are$ (1) $3 β -particles$ (2) $2β-particles and 1 α -particle$ (3) $2β-particles and 1 γ -particle$ (4) $2 α -particles and 1 β -particle.$ 82. $The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an$ (1) $isomer of parent$ (2) $isotone of parent$ (3) $isotope of parent$ (4) $isobar of parent$ 83. $What will be the energy released in joule, in the process of fission by 1 mg of_{92}^{240} U . Assume energy release per fission is 200 MeV . [use Avogadro's number as 6 \times 10^{23} and 1 eV = 1.6 \times (10^{- 19} J)$ (1) $6.2 \times 10^{7} J$ (2) $7.0 \times 10^{7} J$ (3) $8.0 \times 10^{7} J$ (4) $8.2 \times 10^{7} J$ 84. $When an α -particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as [NEET 2016]$ (1) $\frac{1}{m}$ (2) $\frac{1}{m ^{2}}$ (3) $m$ (4) $\frac{1}{m}$ 85. $The half-life of tritium is 12.5 years. What mass of tritium of initial mass 64 mg will remain undecayed after 50 years?$ (1) $32 mg$ (2) $8 mg$ (3) $16 mg$ (4) $4 mg$ 86. $Radiation coming from transitions n = 2 to n = 1 of hydrogen atoms fall on H e^{+} ions in n = 1 and n = 2 states. The possible transition of helium ions as they absorb energy from the radiation is:$ (1) $n = 2 \to n = 3$ (2) $n = 1 \to n = 4$ (3) $n = 2 \to n = 5$ (4) $n = 2 \to n = 4$ 87. $A radioactive sample S_{1} having the activity A_{1} has twice the number of nuclei as another sample S_{2} of activity A_{2} . If A_{2} = 2 A_{1}, then the ratio of half life of S_{1} to the life of S_{2} is$ (1) $4$ (2) $2$ (3) $0.25$ (4) $0.75$ 88. $A radioactive substance of half life 138.6 days is placed in a box. After n days only 20 % of the substance is present then the value of n is [ln (5) = 1.61]$ (1) $693$ (2) $138.6$ (3) $277.2$ (4) $322$ 89. $A radio-active sample of half-life 10 days contains 1000 x nuclei. Number of original nuclei present after 5 days is$ (1) $707 x$ (2) $750 x$ (3) $500 x$ (4) $250 x$ 90. $There are 1 0^{10} radioactive nuclei in a given radioactive element, its half-life time is 1 minute. How many nuclei will remain after 30 seconds? (2 = 1.414)$ (1) $2 \times 1 0^{10}$ (2) $7 \times 1 0^{9}$ (3) $1 0^{5}$ (4) $4 \times 1 0^{10}$