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Set 2 of 14 · Questions 31-60 of 394

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Mere Teacher · Previous Year Questions NEET Physics · Atoms · Set 2 (Q31-60)
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31. $A particle A of mass ' m' and charge ' q' is accelerated by a potential difference of 50 V . Another particle B of mass 4 m and charge q is accelerated by a potential difference of 2500 V . The ratio of de-Broglie wavelengths \frac{λ _{A}}{λ _{B}} is close to :$ (1) $14.14$ (2) $10.00$ (3) $0.07$ (4) $4.47$ 32. $The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is$ (1) $1 : 1$ (2) $1 : - 1$ (3) $2 : - 1$ (4) $1 : - 2$ 33. $7.9 MeVα -particle scatters from a target material of atomic number 79. From the given data the estimated diameter of nuclei of the target material is (approximately)____m. (\frac{1}{4 π ϵ _{o}} = 9 \times 10^{9} Nm^{2} / C^{2}) and electron charge (= 1.6 \times 10^{- 19} C)$ (1) $1.44 \times 10^{- 13}$ (2) $5.76 \times 10^{- 14}$ (3) $2.88 \times 10^{- 14}$ (4) $1.69 \times 10^{- 12}$ 34. $If the momentum of electron is changed by P, then the de Broglie wavelength associated with it changes by 0.5 % . The initial momentum of electron will be:$ (1) $200 P$ (2) $400 P$ (3) $\frac{P}{200}$ (4) $100 P$ 35. $In the Bohr model of a hydrogen atom, the centripetal force is furnished by the coulomb attraction between the proton and the electron. If a_{0} is the radius of the ground state orbit, m is the mass and e is the charge on the electron and ϵ_{0} is the vacuum permittivity, the speed of the electron is$ (1) $\frac{e}{4 π ϵ _{0} a _{0} m}$ (2) $\frac{e}{ϵ _{0} a _{0} m}$ (3) $0$ (4) $\frac{4 π ϵ _{0} a _{0} m}{e}$ 36. $The energy of a hydrogen atom in the ground state is - 13.6 eV The energy of a H e^{+} ion in the first excited state will be$ (1) $- 13.6 eV$ (2) $- 27.2 eV$ (3) $- 54.4 eV$ (4) $- 6.8 eV$ 37. $An electron of mass m and magnitude of charge \|e\| initially at rest gets accelerated by a constant electric field E . The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is:$ (1) $- \frac{h}{\| e \| Et}$ (2) $- \frac{h}{( e ) E t}$ (3) $- \frac{h}{( e ) E t ^{2}}$ (4) $\frac{( e ) Et}{h}$ 38. $If an alpha particle with energy 7.7 MeV is bombarded on a thin gold foil, the closest distance from nucleus it can reach is____m. (Atomic number of gold = 79 and \frac{1}{4 π ϵ _{o}} = 9 \times 10^{9} in SI units)$ (1) $3.85 \times 10^{- 16}$ (2) $3.85 \times 10^{- 14}$ (3) $2.95 \times 10^{- 16}$ (4) $2.95 \times 10^{- 14}$ 39. $A radioactive nucleus can decay by two different processes. Half-life for the first process is 3.0 hours while it is 4.5 hours for the second process. The effective half- life of the nucleus will be:$ (1) $3.75 hours$ (2) $0.56 hours$ (3) $0.26 hours$ (4) $1.80 hours$ 40. $The wavelength of the first line in Balmer series in the hydrogen spectrum is ' λ'. What is the wavelength of the second line in the same series?$ (1) $\frac{20}{27} λ$ (2) $\frac{3}{16} λ$ (3) $\frac{5}{36} λ$ (4) $\frac{3}{4} λ$ 41. $Given below are two statements: Statement I: For all elements, greater the mass of the nucleus, greater is the binding energy per nucleon. Statement II: For all elements, nuclei with less binding energy per nucleon transforms to nuclei with greater binding energy per nucleon. In the light of the above statements, choose the correct answer from the options given below$ (1) $Statement I is true but Statement II is false$ (2) $Both Statement I and Statement II are true$ (3) $Both Statement I and Statement II are false$ (4) $Statement I is false but Statement II is true$ 42. $The nuclei_{6} C^{13} and_{7} N^{14} can be described as$ (1) $isotones$ (2) $isobars$ (3) $isotopes of carbon$ (4) $isotopes of nitrogen$ 43. $What is the half-life period of a radioactive material if its activity drops to 1/ 1 6^{t h} of its initial value of 30 years?$ (1) $9.5 years$ (2) $8.5 years$ (3) $7.5 years$ (4) $10.5 years$ 44. $The shortest wavelength in the Paschen series of the Hydrogen spectrum is Rydberg constant of hydrogen = 1.097 \times 10^{7} m^{- 1} .$ (1) $91.2 nm$ (2) $364.6 nm$ (3) $820.4 nm$ (4) $2278.9 nm$ 45. $A nucleus has mass number α and radius R_{α} . Another nucleus has mass number β and radius R_{β} . If β = 8 α then R_{α} / R_{β} is:$ (1) $8$ (2) $0.5$ (3) $2$ (4) $1$ 46. $The time period of revolution of electron in its ground state orbit in a hydrogen atom is 1.6 \times 10^{- 16} s . The frequency of revolution of the electron in its first excited state (in s^{- 1}) is:$ (1) $7.8 \times 10^{14}$ (2) $7.8 \times 10^{16}$ (3) $3.7 \times 10^{14}$ (4) $3.7 \times 10^{16}$ 47. $An electron makes a transition from orbit n = 4 to the orbit n = 2 of a hydrogen atom. What is the wavelength of the emitted radiations? (R = Rydberg ’ s constant)$ (1) $\frac{16}{4 R}$ (2) $\frac{16}{5 R}$ (3) $\frac{16}{2 R}$ (4) $\frac{16}{3 R}$ 48. $The ratio of wavelength for transition of electrons from 2^{nd} orbit to 1^{st} orbit of Helium (He^{4 +}) and Lithium (Li^{+++}) is (Atomic number of Helium = 2, Atomic number of Lithium = 3)$ (1) $9 : 4$ (2) $4 : 9$ (3) $9 : 36$ (4) $2 : 3$ 49. $v_{1} is the frequency of the series limit of Lyman series, v_{2} is the frequency of the first line of Lyman series and v_{3} is the frequency of the series limit of the Balmer series. Then$ (1) $v_{1} - v_{2} = v_{3}$ (2) $v_{1} = v_{2} - v_{3}$ (3) $\frac{1}{v _{2}} = \frac{1}{v _{1}} + \frac{1}{v _{3}}$ (4) $\frac{1}{v _{1}} = \frac{1}{v _{2}} + \frac{1}{v _{3}}$ 50. $An electron revolving in n^{th} Bohr orbit has magnetic moment μ_{n} . If μ_{n} α n^{x}, the value of x is:$ (1) $2$ (2) $1$ (3) $3$ (4) $0$ 51. $In an electron microscope, the resolution that can be achieved is of the order of the wavelength of electrons used. The resolve a width of 7.5 \times 10^{- 12} m, the minimum electron energy required is close to :$ (1) $500 keV$ (2) $25 keV$ (3) $1 keV$ (4) $100 keV$ 52. $The frequency of revolution of the electron in Bohr's orbit varies with n, the principal quantum number as$ (1) $\frac{1}{n ^{4}}$ (2) $\frac{1}{n ^{2}}$ (3) $\frac{1}{n}$ (4) $\frac{1}{n ^{3}}$ 53. $Given below are two statements: Statement I: Most of the mass of the atom and all its positive charge are concentrated in a tiny nucleus and the electrons revolve around it, is Rutherford's model. Statement II: An atom is a spherical cloud of positive charges with electrons embedded in it, is a special case of Rutherford's model. In the light of the above statements, choose the most appropriate from the options given below.$ (1) $Both statement I and statement II are false$ (2) $Statement I is false but statement II is true$ (3) $Statement I is true but statement II is false$ (4) $Both statement I and statement II are true$ 54. $When a uranium isotope_{92}^{235} U is bombarded with a neutron, it generates_{36}^{89} Kr, three neutrons and [NEET 2020]$ (1) $_{40}^{91} Zr$ (2) $_{36}^{101} Kr$ (3) $_{36}^{103} Kr$ (4) $_{56}^{144} Ba$ 55. $The de Broglie wavelength of an electron in 4^{th} orbit is (r = radius of 1^{st} orbit)$ (1) $2 πr$ (2) $4 πr$ (3) $8 πr$ (4) $16 πr$ 56. $A radiation of energy ' E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light):$ (1) $\frac{2 E}{C}$ (2) $\frac{2 E}{C ^{2}}$ (3) $\frac{E}{C ^{2}}$ (4) $\frac{E}{C}$ 57. $Find the ratio of energies of photons produced due to transition of an election of hydrogen atom from its (i) second permitted energy level to the first level, and (ii) the highest permitted energy level to the first permitted level.$ (1) $3 : 4$ (2) $4 : 3$ (3) $1 : 4$ (4) $4 : 1$ 58. $In Balmer series, wavelength of first line is λ_{1} and in Brackett series wavelength of first line is λ_{2}, then λ_{1} / λ_{2} is$ (1) $0.162$ (2) $0.124$ (3) $0.138$ (4) $0.188$ 59. $For a nucleus of mass number A and radius R, the mass density of nucleus can be represented as$ (1) $A^{\frac{2}{3}}$ (2) $Independent of A$ (3) $A^{3}$ (4) $A^{\frac{1}{3}}$ 60. $In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by:$ (1) $increasing the potential difference between the anode and filament$ (2) $increasing the filament current$ (3) $decreasing the filament current$ (4) $decreasing the potential difference between the anode and filament$