Title 13.NUCLEI - Questions.pdf ✅

13.NUCLEI (1.)1 g of hydrogen is converted into 0.993 g of helium in a thermonuclear reaction. The energy released is (a.) 63 × 107 J (b.) 63 × 1010J (c.) 63 × 1014J (d.) 63 × 1020J (2.)If the binding energy per nucleon in 3Li 7 and 2He 4nuclei are respectively 5.60 MeV and 7.06 MeV, then the energy of proton in the reaction 3Li + p → 22He 4 is (a.) 19.6 MeV (b. ) 2.4 MeV (c.) 8.4 MeV (d. ) 17.3 MeV (3.)The energy released in the fission of 1Kg of 92U 235 is (energy per fission =200 MeV) (a.) 5.1 × 1026eV (b. ) 5.1 × 1026 J (c.) 8.2 × 1013 J (d. ) 8.2 × 1013 MeV (4.)An electron jumps from the 4 th orbit to the 2 nd orbit of hydrogen atom. Given the Rydberg’s constant R = 105 cm−1 . The frequency in Hz of the emitted radiation will be (a.) 3 16 × 105 (b.) 3 16 × 1015 (c.) 9 16 × 1015 (d.) 3 4 × 1015 (5.)The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegration in 24 hours is (a.) 2000 (b.) 3000 (c.) 4000 (d.) 5000 (6.)The fact that photons carry energy was established by (a.) Doppler’s effect (b.) Compton’s effect (c.) Bohr’s theory (d.) Diffraction of light (7.)Half-life of radioactive substance is 3.20 h. What is the time taken for a 75% of substance to be used? (a.) 6.38 h (b.) 12 h (c.) 4.18 day (d.) 1.2 day (8.)The half-life of a radioactive element is 3.8 days. The fraction left after 19 days will be (a.) 0.124 (b.) 0.062 (c.) 0.093 (d.) 0.031 (9.)The count rate of a Geiger-Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to 5 s −1 after 2 hours. The initial count rate was (a.) 25 s −1 (b.) 80 s −1 (c.) 625 s −1 (d.) 20 s −1 (10.)If 92U 238 undergoes successively 8 α-decays and 6 β-decays, then resulting nucleus is (a.) 82U 206 (b.) 82Pb206 (c.) 82U 210 (d.) 82U 214 (11.)Excitation energy of a hydrogen like ion in its first excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is (a.) 54.4 eV (b.) 13.6 eV (c.) 40.8 eV (d.) 27.2 eV (12.)A radioactive element 90X 238 decays into 83Y 222. The number of β −particles emitted are (a.) 4 (b.) 6 (c.) 2 (d.) 1 (13.)1 atomic mass unit is equal to (a.) 1 25 (mass of F2 molecule) (b.) 1 14 (mass of N2 molecule) (c.) 1 12 (mass of one C-atom) (d.) 1 16 (mass of O2 molecule) (14.)U 238 decays into Th 234 by the emission of an α −particle. There follows a chain of further radioactive decays, either by α −decay or by β −decay. Eventually a stable nuclide is reached and after that, no further radioactive decay is possible. Which of the following stable nuclides is the end product of the U 238 radioactive decay chain
(a.) Pb 206 (b.) Pb 207 (c.) Pb 208 (d.) Pb 209 (15.)Binding energy per nucleon plot against the mass number for stable nuclei is shown in the figure. which curve is correct (a.) A (b.) B (c.) C (d.) D (16.)The rest energy of an electron is (a.) 510 KeV (b.) 931 KeV (c.) 510 MeV (d.) 931 MeV (17.)In hydrogen atom, electron makes transition from n = 4 to n = 1 level. Recoil momentum of the H atom will be (a.) 3.4 × 10−27N − s (b.) 6.8 × 10−27N − s (c.) 3.4 × 10−24N − s (d.) 6.8 × 10−24N − s (18.)Nuclear fission experiments show that the neutrons split the uranium nuclei into two fragments of about same size. This process is accompanised by the emission of several (a.) Protons and positrons (b.) α-particles (c.) Neutrons (d.) Protons and α-particles (19.)According to the Rutherford’s atomic model, the electrons inside the atom are (a.) Stationary (b.) Not stationary (c.) Centralized (d.) None of these (20.)Which of the following rays are not electromagnetic waves (a.) γ-rays (b.) β-rays (c.) Heat rays (d.) X-rays (21.)The first line in the Lyman series has wavelength λ. The wavelength of the first line in Balmer series is (a.) 2 9 λ (b.) 9 2 λ (c.) 5 27 λ (d.) 27 5 λ (22.)Best neutron moderator is (a.) Beryllium oxide (b.) Pure water (c.) Heavy water (d.) Graphite (23.)Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Bohr’s atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength λ (given in terms of the Rydberg constant R for the hydrogen atom) is equal to (a.) 9/(5R) (b.) 36/(5R) (c.) 18/(5R) (d.) 4/R (24.)The half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its 1 16 th part (a.) 12 h (b.) 16 h (c.) 48 h (d.) 192 h (25.)The fussion process is possible at high temperatures, because at higher temperatures (a.) The nucleus disintegrates (b.) The molecules disintegrates (c.) Atom become ionized (d.) The nucleus get sufficient energy to overcome the strong forces of repulsion (26.)In half life of a radio isotope is 2 seconds and number of atoms are only 4, then after one half life remaining (without decay) atoms are probably (a.) 1 (b.) 2 (c.) 3 (d.) All the above (27.)The correct order of ionizing capacity of α, β and γ −rays is (a.) α > γ > β (b.) α > β > γ (c.) α < β < γ (d.) γ > α > β (28.)The example of nuclear fusion is (a.) Formation of Ba and Kr from U 235 (b.) Formation of He from H (c.) Formation of Pu − 235 from U − 235 Binding energy per nucleon Mass number A C B D
(d.) Formation of water from hydrogen and oxygen (29.)Equivalent energy of mass equal to 1 a. m. u. is (a.) 931 KeV (b.) 931 eV (c.) 931 MeV (d.) 9.31 MeV (30.)The ratio of the wavelengths for 2 → 1 transition on Li ++, He + and H is (a.) 1 : 2 : 3 (b.) 1 : 4 : 9 (c.) 4 : 9 : 36 (d.) 3 : 2 : 1 (31.)The ratio of speed of an electron in ground state in Bohrs first orbit of hydrogen atom to velocity of light in air is (a.) e 2 2ε0hc (b.) 2e 2ε0 hc (c.) e 3 2ε0hc (d.) 2ε0hc e 2 (32.)The ratio of half-life times of two elements A and B is TA TB . The ratio of respectively decay constants λA λB is (a.) TB TA (b.) TA TB (c.) TA+TB TA (d.) TA−TB TA (33.)Ionization energy of hydrogen is 13.6 eV. If h = 6.6 × 10−34J − s, the value of R will be of the order of (a.) 1010m−1 (b.) 107m−1 (c.) 104m−1 (d.) 10−7m−1 (34.)Which of the following transitions in a hydrogen atom emits photon of the highest frequency (a.) n = 1 to n = 2 (b.) n = 2 to n = 1 (c.) n = 2 to n = 6 (d.) n = 6 to n = 2 (35.)The ratio between Bohr radii are (a.) 1 : 2 : 3 (b.) 2 : 4 : 6 (c.) 1 : 4 : 9 (d.) 1 : 3 : 5 (36.)Consider a radioactive material of half-life 1.0 minute. If one of the nuclei decays now, the next one will decay (a.) After 1 minute (b.) After 1 loge 2 minute (c.) After 1 N minute, where N is the number of nuclei present at that moment (d.) After any time (37.)The most stable particle in Baryon group is (a.) Proton (b.) Lamda-particle (c.) Neutron (d.) Omega-particle (38.)An artificial radioactive decay series begins with unstable 94 241Pu. The stable nuclide obtained after eight α −decays and five β −decays is (a.) 83 209Bi (b.) 82 209Pb (c.) 82 205Ti (d.) 82 201Hg (39.)A radioactive sample has N0 active atoms t = 0. If the rate of disintegration at any time is R and the number of atoms is N, then the ratio R/N varies with time as (a.) (b.) (c.) (d.) (40.)The mass and energy equivalent to 1 amu are respectively (a.) 1.67 × 10−27gm, 9.30 MeV (b.) 1.67 × 10−27kg, 930 MeV (c.) 1.67 × 10−27kg, 1 MeV (d.) 1.67 × 10−34kg, 1 MeV (41.)The activity of a sample of a radioactive material is A at time t1 and A2 at time t2(t2 > t1). If its mean life is T, then (a.) A1t1 = A2t2 (b.) A1 − A2 = t2 − t1 (c.) A2 = A1e (t1−t2)/T (d.) A2 = A1e (t1/t2)/T O t O t O t O t
(42.)Mean life of a radioactive sample is 100 s. Then its half-life(in minutes) is (a.) 0.693 (b.) 1 (c.) 10−4 (d.) 1.155 (43.)Neutrons are used in nuclear fission, because (a.) Neutrons are attracted by nucleus (b.) Mass of neutrons is greater than protons (c.) Neutrons are neutral and hence are not repelled by the nucleus (d.) Neutrons could be accelerated to a greater energy (44.)In hydrogen atom, the electron is moving round the nucleus with velocity 2.18 × 106m/s in an orbit of radius 0.528Å. The acceleration of the electron is (a.) 9 × 1018m/s 2 (b.) 9 × 1022m/s 2 (c.) 9 × 10−22m/s 2 (d.) 9 × 1012m/s 2 (45.)A count rate metre shows a count of 240 per minute from a given radioactive source later the metre shows a count rate 0f 30 min −1 . The half-life of the source is (a.) 80 min (b.) 120 min (c.) 20 min (d.) 30 min (46.)99% of a radioactive element will decay between (a.) 6 and 7 half lives (b.) 7 and 8 half lives (c.) 8 and 9 half lives (d.) 9 half lives (47.)A moderator is used in nuclear reactors in order to (a.) Slow down the speed of the neutrons (b.) Accelerate the neutrons (c.) Increase the number of neutrons (d.) Decrease the number of neutrons (48.)The frequency of 1st line of Balmer series in H2 atom is v0. The frequency of line emitted by singly ionized He atom is (a.) 2v0 (b.) 4v0 (c.) v0/2 (d.) v0/4 (49.)In the nuclear fusion reaction 1H 2 + 1H 3 → 2He 4 + n given that the repulsive potential energy between the two nuclei is 7.7 × 10−14 J, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann’s constant k = 1.38 × 10−23 JK −1 ] (a.) 107 K (b. ) 105 K (c.) 103 K (d. ) 109 K (50.)Consider a hypothetical annihilation of a stationary electron with a stationary positron. What is the wavelength of resulting radiation (h = Planck’s constant, c = speed of light, m0 = rest mass) (a.) h 2m0c (b.) h m0c (c.) 2h m0c (d.) h m0c 2 (51.)Light energy emitted by stars is due to (a.) Breaking of nuclei (b.) Joining of nuclei (c.) Burning of nuclei (d.) Reflection of solar light (52.)Fpe represents electrical force on proton due to electron and Fepon electron due to proton in a hydrogen atom.Similarly Fpe represents the gravitational force on proton due to electron and Fep the corresponding force on electron due to proton. Which of the following is not true? (a.) FPe + Fep = 0 (b. ) F’Pe + F’ep = 0 (c.) FPe + F’Pe + Fep + F’ep = 0 (d. ) FPe + F’Pe = 0 (53.)The rad is the correct unit used to report the measurement of (a.) The ability of a beam of gamma ray photons to produce ions in a target (b.) The energy delivered by radiation to a target (c.) The biological effect of radiation (d.) The rate of decay of a radioactive source (54.)When 88Ra 236 decays in a series by emission of 3α-particles and one β-particle, isotope X formed is (a.) 83X 224 (b. ) 84X 218 (c.) 84X 220 (d. ) 82X 223 (55.)At a given instant there are 25% undecayed radioactive nuclei. After 10 s the number of undecayed nuclei reduces to 6.25%, the mean life of the nuclei is (a.) 14.43 s (b.) 7.21 s (c.) 5 s (d.) 10 s