Atoms PYQs Set 14 (PDF)

Set 14 of 16 · Questions 391-420 of 453

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Mere Teacher · Previous Year Questions JEE Main Physics · Atoms · Set 14 (Q391-420)
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391. $The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between$ (1) $n = 3 to n = 1 states$ (2) $n = 2 to n = 1 states$ (3) $n = 4 to n=3 states$ (4) $n = 3 to n = 2 states$ 392. $Energy levels A, B and C of a certain atom corresponding to increasing values of energy i.e., E_{A} < E_{B} < E_{C} . If λ_{1}, λ_{2} and λ_{3} are wavelengths of radiations corresponding to transitions C to B, B to A and C to A respectively, which of the following relations is correct?$ (1) $λ_{3} = λ_{1} + λ_{2}$ (2) $λ_{3} = \frac{λ _{1} λ _{2}}{λ _{1} + λ _{2}}$ (3) $λ_{1} + λ_{2} + λ_{3} = 0$ (4) $λ_{3}^{2} = λ_{1}^{2} + λ_{2^{2}}$ 393. $An electron, a doubly ionized helium ion (He^{++}) and a proton are having the same kinetic energy. The relation between their respective de-Broglie wavelengths ⋋_{e}, ⋋_{H e^{+}} and ⋋_{p} is$ (1) $λ_{e} > λ_{H e^{++}} > λ_{p}$ (2) $λ_{e} < λ_{p} < λ_{H e^{++}}$ (3) $λ_{e} > λ_{p} > λ_{H e^{++}}$ (4) $λ_{e} < λ_{H e^{++}} = λ_{p}$ 394. $When a certain photosensitive surface is illuminated with monochromatic light of frequency ν, the stopping potential for the photo current is - \frac{V _{0}}{2} . When the surface is illuminated by monochromatic light of frequency \frac{ν}{2}, the stopping potential is - V_{0} . The threshold frequency for photoelectric emission is :$ (1) $\frac{4}{3} ν$ (2) $2 ν$ (3) $\frac{3 ν}{2}$ (4) $\frac{5 ν}{3}$ 395. $X (n, α)_{3}^{7} Li, then X will be$ (1) $_{5}^{10} B$ (2) $_{5}^{9} B$ (3) $_{4}^{11} Be$ (4) $_{2}^{4} He$ 396. $An electron is moving initially with velocity v_{0} i + v_{0} j in uniform electric field E = - E_{0} k . If initial wavelength of electron is λ_{0}, its wavelength at time t is:$ (1) $\frac{⋋ _{0}}{1 + \frac{e ^{2} E _{0}^{2}}{2 m ^{2} v _{0}^{2}} t ^{2}}$ (2) $\frac{⋋ _{0}}{2 + \frac{e ^{2} E _{0}^{2}}{m ^{2} v _{0}^{2}} t ^{2}}$ (3) $\frac{⋋ _{0} m v _{0}}{e E _{0} t}$ (4) $\frac{2 ⋋ _{0} m v _{0}}{e E _{0} t}$ 397. $Given below are two statements: one is labelled as Assertion (a)and the other is labelled as Reason (R). Assertion (A): The density of the copper (_{29}^{64} Cu) nucleus is greater than that of the carbon (_{6}^{12} C) nucleus. Reason (R): The nucleus of mass number A has a radius proportional to A^{1/3} . In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $(A) is correct but (R) is not correct$ (2) $Both (A)and (R) are correct but (R) is not the correct explanation of (A)$ (3) $(A)is not correct but (R) is correct$ (4) $Both (A)and (R) are correct and (R) is the correct explanation of (A)$ 398. $Considering Bohr's atomic model for hydrogen atom: (A) the energy of H atom in ground state is same as energy of He+ion in its first excited state.(B) the energy of H atom in ground state is same as that for Li++ion in its second excited state.(C) the energy of H atom in its ground state is same as that of He+ion for its ground state.(D) the energy of He+ion in its first excited state is same as that for Li++ion in its ground state. Choose the correct answer from the options given below:$ (1) $(A), (B)only$ (2) $(A), (D)only$ (3) $(A), (C)only$ (4) $(B), (D)only$ 399. $Surface of certain metal is first illuminated with light of wavelength λ_{1} = 350 nm and then, by light of wavelength λ_{2} = 540 nm . It is found that the maximum speed of the photo electrons in the two cases differ by a factor of 2 . The work function of the metal (in eV ) is close to : (Energy of photon = \frac{1240}{λ ( in nm )} eV)$ (1) $2.5$ (2) $5.6$ (3) $1.4$ (4) $1.8$ 400. $Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the photoemissive substance. Reason (R): A negative electric potential, which stops the emission of electrons from the surface of a photoemissive substance, varies linearly with frequency of incident radiation. choose the most appropriate answer from the options given below :$ (1) $(A) is false but (R) is true$ (2) $(A) is true but (R) is false$ (3) $Both (A) and (R) are true and (R) is the correct explanation of (A)$ (4) $Both (A) and (R) are true but (R) is not the correct explanation of (A)$ 401. $Solar spectrum is an example for$ (1) $band absorption spectrum$ (2) $line absorption spectrum$ (3) $line emission spectrum$ (4) $continuous emission spectrum.$ 402. $The binding energy for the following nuclear reactions are expressed in MeV ._{2} He^{3} +_{0} n^{1} \to_{2} He^{4} + 20 MeV_{2} He^{4} +_{0} n^{1} \to_{2} He^{5} - 0.9 MeV If X_{3}, X_{4}, X_{5} denote the stability of_{2} He^{3},_{2} He^{4} and_{2} He^{5}, respectively, then the correct order is :$ (1) $X_{4} < X_{5} < X_{3}$ (2) $X_{4} > X_{5} > X_{3}$ (3) $X_{4} > X_{5} < X_{3}$ (4) $X_{4} = X_{5} = X_{3}$ 403. $Frank and Hertz experiment proves that$ (1) $light move in the form of waves as well as particles$ (2) $the electron does not radiate energy, while moving in an orbit$ (3) $the energy states of an atom are quantised$ (4) $the whole of the positive charge of the atom is concentrated in the nucleus$ 404. $1 curie represents$ (1) $3.7 \times 10^{7} disintegrations per second$ (2) $3.7 \times 10^{10} disintegrations per second$ (3) $10^{6} disintegrations per second$ (4) $1 disintegration per second$ 405. $Hydrogen (_{1} H^{1}), Deuterium (_{1} H^{2}), singly ionised Helium (_{2} He^{4})^{+} and doubly ionised lithium (_{3} Li^{6})^{++} all have one electron around the nucleus. Consider an elelctron transition from n = 2 to n = 1 . If the wave lengths of emitted radiation are λ_{1}, λ_{2}, λ_{3}, and λ_{4} respectively then approximately which one of the following is correct?$ (1) $4 λ_{1} = 2 λ_{2} = 2 λ_{3} = λ_{4}$ (2) $λ_{1} = 2 λ_{2} = 2 λ_{3} = λ_{4}$ (3) $λ_{1} = λ_{2} = 4 λ_{3} = 9 λ_{4}$ (4) $λ_{1} = 2 λ_{2} = 3 λ_{3} = 4 λ_{4}$ 406. $For a nucleus_{Z}^{A} X having mass number A and atomic number Z (A) The surface energy per nucleon (b_{s}) = - a_{1} A^{\frac{2}{3}} (B) The Coulomb contribution to the binding energy b_{c} = - a_{2} \frac{Z ( Z - 1 )}{A ^{\frac{4}{3}}} (C) The volume energy b_{v} = a_{3} A (D) Decrease in the binding energy is proportional to surface area. (E) While estimating the surface energy, it is assumed that each nucleon interacts with 12 nucleons. (a_{1}, a_{2} and a_{3} are constants) Choose the most appropriate answer from the options given below:$ (1) $B, C, E only$ (2) $C, D only$ (3) $A, B, C, D only$ (4) $B, C only$ 407. $When photon of energy 4.0 eV strikes the surface of a metal A , the ejected photoelectrons have maximum kinetic energy T_{A} eV and de-Broglie wavelength λ_{A} . The maximum kinetic energy of photoelectrons liberated from another metal B by photon of energy 4.50 eV is T_{B} = (T_{A} - 1.5) eV . If the de-Broglie wavelength of these photoelectrons λ_{B} = 2 λ_{A}, then the work function of metal B is:$ (1) $2 eV$ (2) $3 eV$ (3) $1.5 eV$ (4) $4 eV$ 408. $The energy released in the fusion of 2 kg of hydrogen deep in the sun is E_{H} and the energy released in the fission of 2 kg of^{235} U is E_{U} . The ratio \frac{E _{H}}{E _{U}} is approximately: (Consider the fusion reaction as 4 ∣ H + 2 e^{-} \to_{2}^{4} He + 2 v + 6 γ + 26.7 MeV, energy released in the fission reaction of^{235} U is 200 MeV per fission nucleus and N_{A} = 6.023 \times 10^{23})$ (1) $7.62$ (2) $25.6$ (3) $15.04$ (4) $9.13$ 409. $The Bohr model of atoms$ (1) $Assumes that the angular momentum of electrons is quantized.$ (2) $Uses Einstein’s photoelectric equation.$ (3) $Predicts continuous emission spectra for atoms.$ (4) $Predicts the same emission spectra for all types of atoms.$ 410. $The principle of LASER action involves$ (1) $amplification of particular frequency emitted by the system$ (2) $population inversion$ (3) $stimulated emission$ (4) $all of these.$ 411. $Match the LIST-I with LIST-II List - I A._{0}^{1} n +_{92}^{235} U \to_{54}^{140} Xe +_{38}^{94} Sr + 2_{0}^{1} n B. 2 H_{2} + O_{2} \to 2 H_{2} O C._{1}^{2} H +_{1}^{2} H \to_{2}^{3} He +_{0}^{1} n D._{1}^{1} H +_{1}^{3} H \to_{1}^{2} H +_{1}^{2} H List - II I. Chemical reaction II. Fusion with +ve Q value III. Fission IV. Fusion with -ve Q value Choose the correct answer from the options given below$ (1) $A-II, B-I, C-III, D-IV$ (2) $A-III, B-I, C-II, D-IV$ (3) $A-III, B-I, C-IV, D-II$ (4) $A-II, B-I, C-IV, D-III$ 412. $To explain his theory, Bohr used$ (1) $conservation of linear momentum$ (2) $quantization of angular momentum$ (3) $conservation of quantum frequency$ (4) $none of these$ 413. $The minimum energy required by a hydrogen atom in ground state to emit radiation in Balmer series is nearly:$ (1) $1.5 eV$ (2) $13.6 eV$ (3) $1.9 eV$ (4) $12.1 eV$ 414. $As per given figure A, B and C are the first, second and third excited energy levels of hydrogen atom respectively. If the ratio of the two wavelengths (i . e . \frac{λ _{1}}{λ _{2}}) is \frac{7}{4 n}, then the value of n will be$ 415. $Assume that protons and neutrons have equal masses. Mass of a nucleon is 1.6 \times 1 0^{- 27} kg and radius of nucleus is 1.5 \times 1 0^{- 15} A^{1/3} m. The approximate ratio of the nuclear density and water density is n \times 1 0^{13} . The value of n is_______.$ 416. $Nucleus A having Z = 17 and equal number of protons and neutrons has 1.2 MeV binding energy per nucleon. Another nucleus B of Z = 12 has total 26 nucleons and 1.8 MeV binding energy per nucleons. The difference of binding energy of B and A will be____MeV.$ 417. $A particle of mass 200 MeV / c^{2} collides with a hydrogen atom at rest. Soon after the collision the particle comes to rest, and the atom recoils and goes to its first excited state. The initial kinetic energy of the particle (in eV) is \frac{N}{4} . The value of N is (Given the mass of the hydrogen atom to be 1 GeV / c^{2})$ 418. $d_{1} and d_{2} are the impact parameters corresponding to scattering angles 6 0^{\circ} and 9 0^{\circ} respectively, when an α particle is approaching a gold nucleus. For d_{1} = x d_{2}, the value of x will be _______.$ 419. $A star has 100 % helium composition. It starts to convert three^{4} He into one^{12} C via triple alpha process as^{4} He +^{4} He +^{4} He \to^{12} C + Q . The mass of the star is 2.0 \times 10^{32} kg and it generates energy at the rate of 5.808 \times 10^{30} W . The rate of converting these^{4} He to^{12} C is n \times 10^{42} s^{- 1}, where n is________[ Take, mass of^{4} He = 4.0026 u, mass of^{12} C = 12 u]$ 420. $In an alpha particle scattering experiment distance of closest approach for the α particle is 4.5 \times 10^{- 14} m . If target nucleus has atomic number 80 , then maximum velocity of α -particle is_________\times 10^{5} m / s approximately. (\frac{1}{4 π ϵ _{0}} = 9 \times 10^{9}) SI unit, mass of α particle (= 6.72 \times 10^{- 27} kg)$