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Set 7 of 16 · Questions 181-210 of 453

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Mere Teacher · Previous Year Questions JEE Main Physics · Atoms · Set 7 (Q181-210)
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181. $An electron of stationary hydrogen atom jumps from 4^{th} energy level to ground level. The velocity that the photon acquired as a result of electron transition will be (h = Planck's constant, R = Rydberg's constant, m = mass of photon)$ (1) $\frac{9 Rh}{16 m}$ (2) $\frac{11 hR}{16 m}$ (3) $\frac{13 hR}{16 m}$ (4) $\frac{15 hR}{16 m}$ 182. $In the Rutherford’s alpha scattering experiment, as the impact parameter increases, the scattering angle of the alpha particle$ (1) $remains the same$ (2) $is always 90^{\circ}$ (3) $decreases$ (4) $increases$ 183. $A radioactive nucleus A with a half life T, decays into a nucleus B. At t = 0, there is no nucleus B. At sometime t, the ratio of the number of B to that of A is 0.3. Then, t is given by:$ (1) $t = \frac{T}{log ( 1.3 )}$ (2) $t = \frac{T}{2} \frac{log 2}{log 1 . 3}$ (3) $t = T \frac{log 1.3}{log 2}$ (4) $t = T log (1.3)$ 184. $The ratio of the magnitude of the kinetic energy to the potential energy of an electron in the 5^{th} excited state of a hydrogen atom is:$ (1) $4$ (2) $\frac{1}{4}$ (3) $\frac{1}{2}$ (4) $1$ 185. $The ratio of minimum wavelengths of Lyman and Balmer series will be$ (1) $5$ (2) $10$ (3) $1.25$ (4) $0.25$ 186. $Ionization potential of hydrogen atom is 13.6 eV Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV According to Bohr’s theory, the spectral lines emitted by hydrogen will be$ (1) $one$ (2) $two$ (3) $three$ (4) $four.$ 187. $When hydrogen atom is in its first excited level, its radius is\dots\dots. of the Bohr radius.$ (1) $twice$ (2) $4 times$ (3) $same$ (4) $half$ 188. $A hydrogen atom in ground state absorbs 10.2 eV of energy. The orbital angular momentum of the electron is increased by$ (1) $3.16 \times 10^{- 34} Js$ (2) $1.05 \times 10^{- 34} Js$ (3) $4.22 \times 10^{- 34} Js$ (4) $2.11 \times 10^{- 34} Js$ 189. $A 200 W sodium street lamp emits yellow light of wavelength 0.6 μ m . Assuming it to be 25 % efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is.$ (1) $1.5 \times 10^{20}$ (2) $6 \times 10^{18}$ (3) $62 \times 10^{20}$ (4) $3 \times 10^{19}$ 190. $The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by:$ (1) $μ_{L} = \frac{e L}{2 m}$ (2) $μ_{L} = - \frac{e L}{2 m}$ (3) $μ_{L} = - \frac{e L}{m}$ (4) $μ_{L} = \frac{e L}{m}$ 191. $A source S_{1} is producing 10^{15} photons per second of wavelength 5000Å . Another source S_{2} is producing 1.02 \times 10^{15} photons per second of wavelength 5100Å . Then (power of S_{2})/(power of S_{1}) is equal to$ (1) $1.00$ (2) $1.02$ (3) $1.04$ (4) $0.98$ 192. $The angular momentum for the electron in Bohr's orbit is L. If the electron is assumed to revolve in second orbit of hydrogen atom, then the change in angular momentum will be$ (1) $Zero$ (2) $2L$ (3) $L$ (4) $\frac{L}{2}$ 193. $An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV . If the stopping potential of the photoelectron is 10 V, then the value of n is$ (1) $2$ (2) $3$ (3) $4$ (4) $5$ 194. $As an electron makes a transition from an excited state to the ground state of a hydrogen - like atom/ion:$ (1) $its kinetic energy increases but potential energy and total energy decrease$ (2) $kinetic energy, potential energy and total energy decrease$ (3) $kinetic energy decreases, potential energy increases but total energy remains same$ (4) $kinetic energy and total energy decrease but potential energy increases$ 195. $The half life of a radioactive substance is T. The time taken, for disintegrating (\frac{7}{8})^{th} part of its original mass will be:$ (1) $2T$ (2) $3T$ (3) $T$ (4) $8T$ 196. $An electron in a hydrogen atom undergoes a transition from a higher energy level to a lower energy level. The incorrect statement of the following is$ (1) $Kinetic energy of the electron increases$ (2) $Velocity of the electron increases$ (3) $Angular momentum of the electron remains constant$ (4) $Wavelength of de-Broglie wave associated with the motion of electron decreases$ 197. $A hydrogen like atom has one electron revolving round a stationary nucleus. If the energy required to excite the electron from the 2 nd orbital to 3rd orbit is 47.2 eV, find the atomic number of the given atom.$ (1) $3$ (2) $4$ (3) $5$ (4) $6$ 198. $Atomic weight of Boron is 10.81 and it has two isotopes_{5} B^{10} and_{5} B^{11} . Then the ratio of_{5} B^{10} :_{5} B^{11} in nature would be$ (1) $15 : 16$ (2) $10 : 11$ (3) $19 : 81$ (4) $81 : 19$ 199. $When photon of energy 4.0eV strikes the surface of a metal A, the ejected photoelectrons have maximum kinetic energy T_{A} eV and deBroglie wavelength ⋋_{A} . The maximum kinetic energy of photoelectrons liberated from another metal B by photon of energy 4.50eV is T_{B} = (T_{A} - 1.5)6V. If the DE Broglie wavelength of these photoelectrons ⋋_{B} = 2 ⋋_{A}, then the work function of metal B is:$ (1) $3 eV$ (2) $1.5 eV$ (3) $4.5 eV$ (4) $4 eV$ 200. $Ratio of longest wave lengths corresponding to Lyman and Blamer series in hydrogen spectrum is:$ (1) $\frac{3}{23}$ (2) $\frac{7}{29}$ (3) $\frac{9}{31}$ (4) $\frac{5}{27}$ 201. $The half-life of a radioactive nucleus is 5 years. The fraction of the original sample that would decay in 15 years is:$ (1) $\frac{1}{8}$ (2) $\frac{1}{4}$ (3) $\frac{7}{8}$ (4) $\frac{3}{4}$ 202. $Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively, Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be :$ (1) $4 : 1$ (2) $1 : 4$ (3) $5 : 4$ (4) $1 : 16$ 203. $An excited H e^{+} ion emits two photons in succession, with wavelengths 108.5 nm and 30.4 nm, in making a transition to ground state. The quantum number n, corresponding to its initial excited state is (for photon of wavelength λ, energy E = \frac{1240 eV}{λ ( innm )})$ (1) $n = 4$ (2) $n = 5$ (3) $n = 7$ (4) $n = 6$ 204. $Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr’s atomic model?$ (1) $1.9 eV$ (2) $11.1 eV$ (3) $13.6 eV$ (4) $0.65 eV$ 205. $If ' μ' is the magnetic moment of an electron revolving around hydrogen nucleus in an orbit of principal quantum number ' n', then$ (1) $μ \propto n^{2}$ (2) $μ \propto n$ (3) $μ \propto \frac{1}{n}$ (4) $μ \propto \frac{1}{n ^{2}}$ 206. $A sample of radioactive material A, that has an activity of 10 mCi (1 Ci = 3.7 \times 1 0^{10} decays/s), has twice the number of nuclei as another sample of a different radioactive material B which has an activity of 20 mCi. The correct choices for half-lives of A and B would then be respectively:$ (1) $10 days and 40 days$ (2) $20 days and 5 days$ (3) $5 days and 10 days$ (4) $20 days and 10 days$ 207. $In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is:$ (1) $1.8 V$ (2) $1.2 V$ (3) $0.5 V$ (4) $2.3 V$ 208. $Statement-I: A nucleus having energy E_{1} decays by β^{-} emission to daughter nucleus having energy E_{2}, but the β^{-} rays are emitted with a continuous energy spectrum having end point energy E_{1} - E_{2} . Statement-II: To conserve energy and momentum in β^{-} decay at least three particles must take part in the transformation.$ (1) $Statement-I is correct but statement-II is not correct.$ (2) $Statement-I and statement-II both are correct and statement-II is the correct explanation of statement-I.$ (3) $Statement-I is correct, statement-II is correct and statement-II is not the correct explanation of statement-I$ (4) $Statement-I is incorrect, statement-II is correct.$ 209. $If radius of the_{13}^{27} Al nucleus is taken to be R_{AI}, then the radius of_{53}^{125} Te nucleus is nearly$ (1) $(\frac{53}{13})^{\frac{1}{3}} R_{Al}$ (2) $\frac{5}{3} R_{Al}$ (3) $\frac{3}{5} R_{Al}$ (4) $(\frac{13}{53})^{\frac{1}{3}} R_{Al}$ 210. $\frac{x}{x + 4} is the ratio of energies of photons produced due to transition of an electron of hydrogen atom from its (i) third permitted energy level to the second level and (ii) the highest permitted energy level to the second permitted level. The value of x will be$