Title MODERN PHYSICS III.pdf ✅

Modern Physics  Digital www.allendigital.in [ 259 ] X-RAYS 1. If the K radiation of Mo has a wavelength of 0.71 Å. The wavelength of the corresponding radiation of Cu :– [ZMo = 42, ZCu = 29] (1) 0.52 Å (2) 1.52 Å (3) 2.52 Å (4) 3.52 Å 2. In coolidge tube the potential difference between cathode and anticathode is 120 kV. The maximum energy of emitted X-rays will be: (1) 1.2 × 105 eV (2) 1010 eV (3) 1015 eV (4) 1020 eV 3. If the X–ray tube is working at 25 kV then the minimum wavelength of X–rays will be :– (1) 0.49 Å (2) 0.29 Å (3) 0.19 Å (4)0.39 Å 4. The distance between interatomic lattice planes is 10Å. The maximum wavelength of X–rays which are diffracted by this crystal will be :– (1) 10Å (2) 20Å (3) 30Å (4) 40Å 5. The structure of solids is studied by :– (1) X–rays (2) –rays (3) Cosmic rays (4) Infrared rays 6. 50% of X–rays obtained from a Coolidge tube pass through 0.3 mm. thick aluminium foil. If the potential difference between the target and the cathode is increased, then the fraction of X–rays passing through the same foil will be :– (1) 50% (2) >50% (3) <50% (4) 0% 7. When 50 keV electrons are made incident on a target material, the wavelength of K X–ray line was found to be 0.5Å. When the accelerating potential is increased to 100 kV, then the wavelength of K–line from the same target will be (1) 0.25 Å (2) 0.5 Å (3) 0.75 Å (4) 1.0 Å 8. On increasing the filament current in X-ray tube :– (1) wavelength of X-rays increases (2) penetration power of X-ray increases (3) intensity of X-rays decreases (4) intensity of X-rays increases 9. Which of the following is not affected by electro-magnetic fields :– (1) -rays (2) -rays (3) X-rays (4) cathode-rays 10. Minimum wavelength of X-ray is 2Å, then potential difference between anode and cathode is:– (1) 62 kV (2) 6.2 kV (3) 24.8 kV (4) 2.48 kV 11. X-rays obtained by coolidge tube are :– (1) mono-chromatic (2) of all wavelength below a maximum wavelength (3) of all wavelength above a minimum wave length (4) of all wavelength between a maximum and a minimum wave length 12. X-ray is an electromagnetic radiation, so X-ray photons carry :– (1) an electric charge (2) a magnetic moment (3) both the electric charge and magnetic moment (4) neither electric charge nor magnetic moment 13. Characteristic X-rays are not obtained in the spectrum of H-atom because :– (1) hydrogen is a gas (2) hydrogen is very light (3) energy difference in energy levels of hydrogen is much less (4) energy difference in energy levels of hydrogen is much high 14. Which of the following is related with characteristic emission of X-ray :– (1) -particle emission (2) electron emission (3) positron emission (4) K-electron capturing 15. Penetration power of X-rays depend on :– (1) current flowing in filament (2) applied potential difference (3) nature of target (4) all of the above Exercise - I
NEET : Physics [ 260 ] www.allendigital.in  Digital 16. Which of the following have velocity equal to light (1) cathode rays (2) anode rays (3) X-rays (4) positive rays 17. The energy of characteristic X-rays photon obtained from coolidge tube comes from :– (1) kinetic energy of incident electron. (2) kinetic energy of free electrons of target material (3) kinetic energy of ions of target material (4) electron transition in target material 18. Absorption of X-ray is maximum in which of the following sheets :– (1) copper (2) gold (3) beryllium (4) lead 19. In X-ray spectrum wave length  of line K depends on atomic number Z as :– (1)   Z2 (2)   (Z–1)2 (3)   1 (Z 1) − (4)   2 1 (Z 1) − 20. If potential difference applied to an X-ray tube is V volt, then minimum wavelength of X-rays produced is about (in Å) :– (1) 1240/V (2) 12400/V (3) 24000/V (4) 12.27/V 21. The minimum wavelength of X-rays produced by electrons accelerated by a potential difference of V volts is equal to :– (1) eV hc (2) eh cV (3) hc eV (4) h V 22. In E.M. waves spectrum X-rays region lies between (1) short radio waves and visible region (2) visible and ultraviolet region (3) gamma rays and ultra-violet region (4) short radio waves and long radio waves 23. If V be the accelerating voltage, then the maximum frequency of continuous X-rays is given by :– (1) eh V (2) hV e (3) eV h (4) h eV 24. The shortest wave length emitted from an X- ray tube depends upon :– (1) the voltage applied to the tube (2) the nature of the gas in the tube (3) the current in the tube (4) the nature of target material 25. In an X-ray tube, the intensity of the emitted X-ray beam is increased by :– (1) increasing the filament current (2) decreasing the filament current (3) increasing the target potential (4) decreasing the target potential 26. In an X-ray tube, electrons accelerated through a potential difference of 15000 V strike a copper target. The speed of the emitted X-rays from the tube is :– [e=charge on electron, m=mass of electron, Z=atomic number of target] (1) 2 2e 1500 m   (2) 2 e 1500 m   (3) 2Ze 1500 m  (4) 3 × 108 m/s 27. The momentum of a photon in an X-ray beam of 10–10 metre wavelength is :– (1) 1.5 × 10–23 kg–m/sec (2) 6.6 × 10–24 kg–m/sec (3) 6.6 × 10–44 kg–m/sec (4) 2.2 × 10–52 kg–m/sec 28. The energy of a photon of light with wavelength 5000Å is approximately x eV. This way the energy of an X-ray photon with wavelength 1Å would be:– (1) x eV 5000 (2) 2 x eV (5000) (3) x × 5000 eV (4) x × (5000)2eV 29. The kinetic energy of an electron which is accelerated through a potential of 100 volts is :– (1) 1.602 × 10–17 joules (2) 418.6 calories (3) 1.16 × 104 eV (4) 6.626 × 10–34 watt-second 30. The wavelength of the most energetic X-ray emitted when a metal target is bombarded by electrons having kinetic energy 100 keV is approximately : (1) 12 Å (2) 4 Å (3) 0.31 Å (4) 0.124 Å 31. For harder X-rays :– (1) the wavelength is higher (2) the intensity is higher (3) the frequency is higher (4) the photon energy is lower
Modern Physics  Digital www.allendigital.in [ 261 ] 32. When cathode rays strike a metal target of high melting point with very high velocity, then :– (1) X-rays are produced (2) -rays are produced (3) -rays are produced (4) ultrasonic waves are produced 33. Penetrating power of X-rays can be increased by (1) increasing the potential difference between anode and cathode (2) decreasing the potential difference between anode and cathode (3) increasing the cathode filament current (4) decreasing the cathode filament current 34. K characteristic X-ray refers to the transition :– (1) n = 2 to n = 1 (2) n = 3 to n = 2 (3) n = 3 to n = 1 (4) n = 4 to n = 2 35. The production of characteristic X-rays is due to:- (1) transfer of momentum in collision of electrons with the target atom (2) transfer of energy in collision of electrons with the target atom (3) the transition of electrons in heavy target atoms from high to low energy level (4) none of these 36. X-rays are produced in X-ray tube operating at a given accelerating voltage. The wavelength of the continuous X-rays has values from :– (1) 0 to  (2) min to , where min > 0 (3) 0 to max. ,where max. <  (4) min to max., where 0 < min < max.<  37. The ratio of the energy of an X-ray photon of wavelength 1 Å to that of visible light of wavelength 5000 Å is :– (1) 1 : 5000 (2) 5000 : 1 (3) 1 : 25 × 106 (4) 25 × 106 38. According to Mosley’s law, the frequency of a characteristic spectral line in X-ray spectrum varies as :– (1) atomic number of the element (2) square of the atomic number of the element (3) square root of the atomic number of the element (4) fourth power of the atomic number of the element 39. For the structural analysis of crystals, X-rays are used because :– (1) X-rays have wavelength of the order of interatomic spacing (2) X-rays are highly penetrating radiations (3) wavelength of X-rays is of the order of nuclear size (4) X-rays are coherent radiations 40. What determines the hardness of the X-rays obtained from the Coolidge tube :– (1) current in the filament (2) pressure of air in the tube (3) nature of target (4) potential difference between cathode and target 41. The most penetrating radiation out of the following is (1) X-rays (2) -rays (3) -particles (4) -rays 42. On increasing the number of electrons striking the anode of an X-ray tube, which one of the following parameters of the resulting X-rays would increase (1) penetration power (2) frequency (3) wavelength (4) intensity 43. For production of characteristics K X-ray, the electron transition will be :– (1) n = 2 to n = 1 (2) n = 3 to n = 2 (3) n = 3 to n = 1 (4) n = 4 to n = 2 44. If X-rays is passed through from strong magnetic field, then X-rays :– (1) will deviate maximum (2) will deviate minimum (3) undeviated (4) none of these 45. Which of the following wavelength is not possible for an X-ray tube which is operated at 40 kV:– (1) 0.25 Å (2) 0.5 Å (3) 0.52 Å (4) 0.34 Å 46. If the operating voltage of X–ray tube is 50 kV then velocity of X–ray :– (1) 4 × 104 m/sec (2) 3 × 108 m/sec (3) 108 m/sec (4) 3 m/sec
NEET : Physics [ 262 ] www.allendigital.in  Digital 47. When X–rays are projected in strong magnetic field it will :– (1) deflect right. (2) deflect left. (3) move in opposite direction to magnetic field (4) not deflect 48. If voltage of X–ray tube is doubled then intensity of X–rays will :– (1) halved (2) remains constant (3) doubled (4) quadrupled 49. If minimum wavelength obtained in a X–ray tube is 2.5 × 10–10 m. For this minimum wavelength the minimum operating voltage of the tube should be– (1) 2 kV (2) 3 kV (3) 4 kV (4) 5 kV 50. In X-ray tube, wavelength of X-ray is the characteristic of :– (1) tube voltage (2) target material (3) filament current (4) none of these 51. 5000V is applied on an electronic X-ray tube. Then minimum wavelength of X-ray will be :– (1) 1.24 × 10–11 m (2) 2.48 × 10–10 m (3) 3.72 × 10–11 m (4) 4.96 × 10–11 m 52. Pressure inside the X-ray tube is :– (1) equal to 740 mm of Hg (2) equal to 76 mm of Hg (3) equal to 10–5 mm of Hg (4) equal to 10–7 mm of Hg 53. 20 kV potential is applied across X-ray tube, the minimum wavelength of X-ray emitted will be :– (1) 0.62 Å (2) 0.37 Å (3) 1.62 Å (4) 1.31 Å 54. What is the minimum wavelength of X–rays :– (1) eV hc (2) hc eV (3) hc e (4) hc V 55. To increase the hardness of X–rays in coolidge tube we should :– (1) increase filament current (2) increase filament voltage (3) increase the voltage applied between cathode and anticathode (4) none of these 56. For X–ray diffraction, order of size of obstacle is : (1) 1 Å (2) 10 Å (3) 20 Å (4) 30 Å 57. Voltage applied across the X-ray tube is (1) 1000 V (2) 100 V (3) 10 V (4) 106 V 58. Which of the following is the wave length of X-ray: (1) 10,000 Å (2) 1000 Å (3) 1 Å (4) 10–4 Å 59. Lattice constant of a crystal is 3 × 10–8 cm and glance angle of X-ray is 30° for first order diffraction, then the value of  will be :– (1) 6 × 10–8 cm (2) 3 × 10–8 cm (3) 1.5 × 10–8 cm (4) 10–8 cm 60. min of X-rays depends on :- (1) Atomic number of target (2) Energy of electron (3) Both (1) & (2) (4) None of these 61. The order of energy of X-ray photon is :- (1) MeV (2) keV (3) eV (4) GeV 62. If vacuum tube is operated at 6.4 kV, what is the wavelength of X-ray produced :- (1) 1.93Å (2) 1.53Å (3) 2.67Å (4) 0.78Å 63. When electron is incident on molyblednum then by changing energy of electron :- (1) min changes (2) min remains constant (3) K  , K  changes (4) min, K  and K  all changes 64. In Coolige tube the relation between used voltage V and minimum wavelength min is- (1) min  V (2) min  V (3) min 1 V   (4) min 1 V   65. In an X–ray tube accelerating potential is 60 kV. What is the maximum frequency of emitted X-ray ? (1) 1.45 × 1019 Hz (2) 1.45 × 1015 Hz (3) 1.25 × 1015 Hz (4) 1.25 × 1013 Hz ATOMIC STRUCTURE 66. What is the wavelength of the least energetic photon emitted in the Lyman series of the hydrogen atom spectrum ? (1) 150 nm (2) 122 nm (3) 102 nm (4) 82 nm