Tiêu đề 12. ATOMS(H).pdf ✅

NEET REVISION 12. ATOMS(H) NEET REVISION Date: March 18, 2025 Dura on: 1:00:00 Total Marks: 180 INSTRUCTIONS INSTRUCTIONS PHYSICS 1. In alpha particle scattering experiment, if is the initial velocity of the particle, then the distance of closest approach is . If the velocity is dou‐ bled, then the distance of closest approach be‐ comes [Q356367] (1) (2) (3) (4) 2. The first line of Balmer series has wavelength 6563 . What will be the wavelength of the first member of Lyman series? [Q356610] (1) 1215.4 (2) 2500 (3) 7500 (4) 600 3. The average of molecules in a gas at tem‐ perature is .Find the temperature at which the average of molecules equal to binding energy of -atom [Q356440] (1) (2) (3) (4) 4. Assuming the atom is in the ground state, the ex‐ pression for the magnetic field at a point nucleus in hydrogen atom due to circular motion of elecr‐ ton is [ permeability of free space, mass of electrons] permittivity of free space, planck's constant] [Q356387] (1) (2) (3) (4) 5. The wavelength of -line characteristic -rays emitted by an element is . The wave‐ length of -line emitted by the same element will be [Q356672] (1) (2) (3) (4) 6. If elements with principal quantum number were not allowed in nature, then the num‐ ber of possible elements would be [Q356542] (1) 32 (2) 60 (3) 18 (4) 4 7. Using Bohr’s quantisation condition, what is the rotational energy in the second orbit for a di‐ atomic molecule? ( moment of inertia of di‐ atomic molecule, Planck’s constant) [Q356516] (1) (2) (3) (4) 8. Electrons in a certain energy level , can emit 3 spectral lines. When they are in another energy level . They can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio [Q356551] (1) (2) (3) (4) 9. If wavelength of photon emitted due to transition of an electron from the third orbit to the first or‐ bit in a hydrogen atom is , then the wavelength of photon emitted due to transition of electrons from the fourth orbit to the second orbit will be times . What is the value of ? [Q356555] (1) (2) (3) (4) 10. An particle of energy is scattered through by gold nucleus. The distance of v d 4d 2d d 2 d 4 A ∘ A ∘ A ∘ A ∘ A ∘ KE T KT 3 2 KE H 1.05 × 10 4K 1.05 × 10 5K 1.05 × 10 3K None of these μ0 → m → [ε0 → h → μ0e 3πm2 8ε0 2h4 μ0e 2πm4 6ε0 3h4 μ0e 7πm2 8ε0 3h 5 μ0e 3πm3 6ε0 3h3 Kα X 0.32 A ∘ Kβ 0.32 A ∘ 0.39 A ∘ 0.49 A ∘ 0.27 A ∘ n > 4 I = h = h 2Iπ2 h 2 2Iπ2 h 2 2I 2π2 h 2I 2π n = n1 n = n2 4 : 3 3 : 4 2 : 1 1 : 2 λ N λ N 2.65 λ 7.35 λ 5.47 λ 4.74 λ α− 5 MeV 180 ∘
NEET REVISION closest approach is of the order of [Q356343] (1) (2) (3) (4) 11. If the electron in hydrogen atom jumps from second Bohr orbit to ground state and difference between energies of the two states is radiated in the form of photons. If the work function of the material is 4.2 , then stopping potential is [energy of electron in orbit ] [Q356544] (1) (2) (3) (4) 12. is given to electron in 4 th orbit, then find its final energy when it comes out of - atom [Q356446] (1) (2) (3) (4) 13. In a hydrogen-like atom electron make transi‐ tion from an energy level with quantum number to another with quantum number . If , the frequency of radiation emitted is proportional to : [Q356497] (1) (2) (3) (4) 14. The ionisation potential of -atom is . When it is excited from ground state by monochromatic radiations of the num‐ ber of emission lines will be (according to Bohr's theory) [Q356587] (1) 10 (2) 8 (3) 6 (4) 4 15. If the wavelength of first transition of the Balmer series is displaced by , then the velocity of the excited hydrogen atoms is found to be . When their radiations are observed at an angle to their motion, then the value of is [Take ] [Q356547] (1) 12.62 (2) 10.78 (3) 16.67 (4) 19.47 16. Magnetic field at the centre (at nucleus) of the hydrogen like atoms (atomic number ) due to the motion of electron in orbit is propor‐ tional to . What is the value of ? [Q356454] (1) 4 (2) 8 (3) 2 (4) 10 17. Consider the spectral line resulting from the transition to in the atoms and the ions given below. The shortest wavelength is produced by [Q356502] (1) Hydrogen atom (2) Deuterium atom (3) Singly ionised helium (4) Doubly ionised lithium 18. The radiation corresponding to transition of hydrogen atom falls on a metal surface to pro‐ duce photoelectrons. These electrons are made to enter a magnetic field of If the ra‐ dius of the largest circular path followed by these electrons is , the work function of the metal is close to : [Q356545] (1) (2) (3) (4) 19. An element of atomic number 9 emits - ray of wavelength . Find the atomic number of the element which emits X-ray of wave‐ length . [Q356673] (1) 3 (2) 1 (3) 5 (4) 7 20. In Bohr model of hydrogen atom, the force on the electron depends on the principal quantum number as [Q356459] (1) (2) (3) (4) does not depend on 21. The transition from the state to in a hydrogen like atom results in ultraviolet radia‐ tion. Infrared radiation will be obtained in the transition from [Q356585] (1) (2) (3) (4) 22. The following diagram indicates the energy lev‐ els of a certain atom when the system moves from level to , a photon of wavelength is emitted. The wavelength of photon produced during its transistion from level to is: [Q356566] (1) (2) (3) (4) 23. What percentage increase in wavelength leads to loss of photon energy in a photon-elec‐ tron collision? [Q356381] (1) (2) 10 −12 cm 10 −16 cm 10 −10 cm 10 −14 cm eV n th = − eV 13.6 n 2 2 V 4 V 6V 8V 15 eV H 14.15 eV 13.6 eV 12.08 eV 15.85 eV n (n − 1) n >> 1 1 n 1 n 2 1 n 3 2 1 n3 H 13.6 V 970.6 A ∘ Δλ = 0.2A ∘ N × 10 3 m/s θ = 60 ∘ N R = 10 7 m−1 = Z n th n pZ q q − p n = 2 n = 1 3 → 2 3 × 10 −4T. 10.0 mm 3.1 eV 2.1 eV 1.1 eV 0.7 eV Kα X λ Kα 4λ n F ∝ 1/n 3 F ∝ 1/n 4 F ∝ 1/n 5 n n = 4 n = 3 2 → 1 3 → 2 4 → 2 5 → 4 2 E E λ 4E 3 E λ 3 3λ 4 4λ 3 3λ 75% 200% 100%
NEET REVISION (3) (4) 24. An electron in Bohr's hydrogen atom has an en‐ ergy of . The angular momentum of the electron is [Q356392] (1) (2) (3) ( is an integer) (4) 25. An electron revolving in Bohr orbit has magnetic moment . If , the value of is [Q356435] (1) 0 (2) 2 (3) 3 (4) 1 26. The shortest wavelenght of Paschen, Balmer and Lyman series are in the ratio: [Q356639] (1) (2) (3) (4) 27. The ratio of the long wavelength limits of the Lyman and Balmer series of hydrogen is [Q356582] (1) (2) (3) (4) 28. An electron in a hydrogen atom makes a transi‐ tion from to . The time period of the electron in the initial state is eight times that in the final state. The possible values of and are: [Q356420] (1) (2) (3) (4) 29. The ground state energy of an atom is . Photon emitted during the transition of electron from to state, is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of . The threshold wavelength of the ma‐ terial used is (Take ] [Q356535] (1) (2) (3) (4) 30. Read the Statement - A and Statement - B care‐ fully to mark correct options given below Statement A : Atoms are electrically neutral as they contain equal number of positive and negative charges. Statement B : Atoms of each element are stable and emit their characteristic spectrum. [Q356487] (1) Statement A is correct but Statement B is incorrect. (2) Statement A is incor- rect but Statement B is correct. (3) Both statements are correct. (4) Both Statements are incorrect. 31. Find the ratio of minimum to maximum wave‐ length of radiation emitted by electron in ground state of Bohr's hydrogen atom. [Q356577] (1) (2) (3) (4) 32. The binding energy of a -atom, considering an electron moving around a fixed nuclei (pro‐ ton), is ( - mass of electron). If one decides to work in a frame of reference where the electron is at rest, the proton would be moving around it. By similar arguments, the binding energy would be ( proton mass). This last expression is not correct because [Q356426] (1) The frame in which the electron is at rest is not inertial. (2) Bohr-quantisation ap- plies only to electron (3) would not be integral (4) The motion of the pro- ton would not be in circu- lar orbits, even approximately. 33. For hydrogen atom, the energy of radiation emitted in the transition from 4 excited state to 2 excited state, according to Bohr’s theory is [Q356558] (1) (2) (3) (4) 34. A hydrogen atom and a ion are both in the second excited state. If and are their re‐ spective electronic angular momenta, and and are their respective energies, then [Q356496] (1) (2) (3) (4) 35. The angular momentum of an electron in first orbit of ion is - [Q356518] (1) (2) (3) (4) 36. One of the lines in the emission spectrum of has the same wavelength as that of the line of Balmer series in hydrogen spectrum. The 67.7% 300% −3.4 eV h π h 2π nh 2π n 2h π n th μn μn ∝ n x x 9 : 1 : 4 1 : 4 : 9 9 : 4 : 1 1 : 9 : 4 27 : 5 5 : 27 4 : 1 1 : 4 n = n1 n = n2 n1 n2 n1 = 4, n2 = 2 n1 = 8, n2 = 2 n1 = 8, n2 = 1 n1 = 6, n2 = 2 −217.8 eV n = 3 n = 1 190.29eV h = 6.62 × 10 −34Js 3750 A ∘ 1275 A ∘ 5347 A ∘ 7255 A ∘ 1 3 3 4 4 7 5 3 H B = ⋅ me 4 8n 2ε 2 0h 2 m B = − ⋅ Me 4 8n 2ε 2 0h 2 M = n th nd 0.567 eV 0.667 eV 0.967 eV 1.267 eV Li++ LH LLi EH ELi LH > LLi and |EH| > |ELi | LH = LLi and |EH| < |ELi| LH = LLi and |EH| > |ELi| LH < LLi and |EH| < |ELi| Li ++ 3 h 2π 9 h 2π h 2π h 6π Li 2+ 2 nd