{"id":12782,"date":"2025-09-23T05:56:37","date_gmt":"2025-09-23T04:56:37","guid":{"rendered":"https:\/\/mcqsadda.com\/?p=12782"},"modified":"2025-10-22T10:28:55","modified_gmt":"2025-10-22T09:28:55","slug":"radioactivity-top-100-mcqs-with-answer-and-explanation-2","status":"publish","type":"post","link":"https:\/\/mcqsadda.com\/index.php\/2025\/09\/23\/radioactivity-top-100-mcqs-with-answer-and-explanation-2\/","title":{"rendered":"Radioactivity Top 100 MCQs With Answer and Explanation"},"content":{"rendered":"\n

1. Radioactivity was discovered by:<\/mark><\/strong>
a) Marie Curie
b) Henri Becquerel
c) Rutherford
d) J.J. Thomson
Answer:<\/strong> b) Henri Becquerel
Explanation:<\/strong> In 1896, Henri Becquerel discovered radioactivity while working with uranium salts.<\/p>\n\n\n\n

2. Marie Curie discovered which radioactive elements?<\/mark><\/strong>
a) Uranium and Thorium
b) Polonium and Radium
c) Uranium and Radium
d) Thorium and Radon
Answer:<\/strong> b) Polonium and Radium
Explanation:<\/strong> Marie and Pierre Curie discovered polonium and radium from pitchblende ore.<\/p>\n\n\n\n

3. Radioactivity is a:<\/mark><\/strong>
a) Physical property
b) Chemical property
c) Nuclear property
d) Mechanical property
Answer:<\/strong> c) Nuclear property
Explanation:<\/strong> Radioactivity originates from the instability of atomic nuclei.<\/p>\n\n\n\n

4. The particles emitted in \u03b1-decay are:<\/mark><\/strong>
a) Electrons
b) Helium nuclei
c) Protons
d) Neutrons
Answer:<\/strong> b) Helium nuclei
Explanation:<\/strong> Alpha particles = 2 protons + 2 neutrons (\u2074\u2082He\u00b2\u207a).<\/p>\n\n\n\n

5. \u03b2-particles are:<\/mark><\/strong>
a) Protons
b) Neutrons
c) Electrons
d) Positrons
Answer:<\/strong> c) Electrons
Explanation:<\/strong> Beta particles are fast-moving electrons emitted from the nucleus.<\/p>\n\n\n\n

6. \u03b3-rays are:<\/mark><\/strong>
a) Particles
b) Electrons
c) Electromagnetic waves
d) Neutrons
Answer:<\/strong> c) Electromagnetic waves
Explanation:<\/strong> Gamma rays are high-energy photons with no mass or charge.<\/p>\n\n\n\n

7. Which radiation has the highest penetrating power?<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) Neutrons
Answer:<\/strong> c) \u03b3-rays
Explanation:<\/strong> \u03b3-rays can penetrate thick lead sheets, unlike \u03b1 and \u03b2.<\/p>\n\n\n\n

8. Which radiation is stopped by a sheet of paper?<\/mark><\/strong>
a) \u03b1-particles
b) \u03b2-particles
c) \u03b3-rays
d) Neutrons
Answer:<\/strong> a) \u03b1-particles
Explanation:<\/strong> Alpha particles have very low penetration and are stopped by paper\/skin.<\/p>\n\n\n\n

9. The charge on \u03b1-particle is:<\/mark><\/strong>
a) +1
b) +2
c) -1
d) 0
Answer:<\/strong> b) +2
Explanation:<\/strong> Alpha particle = 2 protons + 2 neutrons \u2192 net charge +2.<\/p>\n\n\n\n

10. Which radiation has the least ionizing power?<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) Neutrons
Answer:<\/strong> c) \u03b3-rays
Explanation:<\/strong> \u03b3-rays are least ionizing, while \u03b1-rays are most ionizing.<\/p>\n\n\n\n

11. The speed of \u03b2-particles is nearly:<\/mark><\/strong>
a) Speed of sound
b) Speed of light
c) Zero
d) Half of light
Answer:<\/strong> b) Speed of light
Explanation:<\/strong> \u03b2-particles (electrons) move with speed close to that of light.<\/p>\n\n\n\n

12. Which of the following is not a radioactive element?<\/mark><\/strong>
a) Uranium
b) Radium
c) Thorium
d) Aluminium
Answer:<\/strong> d) Aluminium
Explanation:<\/strong> Aluminium is stable, not radioactive.<\/p>\n\n\n\n

13. The SI unit of radioactivity is:<\/mark><\/strong>
a) Curie
b) Becquerel
c) Rutherford
d) Roentgen
Answer:<\/strong> b) Becquerel
Explanation:<\/strong> 1 Bq = 1 disintegration per second (SI unit).<\/p>\n\n\n\n

14. 1 Curie (Ci) is equal to:<\/mark><\/strong>
a) 3.7 \u00d7 10\u00b9\u2070 disintegrations\/sec
b) 1 disintegration\/sec
c) 100 disintegrations\/sec
d) 10\u2076 disintegrations\/sec
Answer:<\/strong> a) 3.7 \u00d7 10\u00b9\u2070 disintegrations\/sec
Explanation:<\/strong> 1 Ci = activity of 1 g radium = 3.7 \u00d7 10\u00b9\u2070 Bq.<\/p>\n\n\n\n

15. Which radiation is used for sterilization of food?<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) Neutrons
Answer:<\/strong> c) \u03b3-rays
Explanation:<\/strong> \u03b3-rays kill bacteria and preserve food.<\/p>\n\n\n\n

16. In \u03b2\u207b-decay, a neutron is converted into:<\/mark><\/strong>
a) Proton + electron + antineutrino
b) Proton + positron + neutrino
c) Proton only
d) Electron only
Answer:<\/strong> a) Proton + electron + antineutrino
Explanation:<\/strong> n \u2192 p + e\u207b + \u1fe1\u2091.<\/p>\n\n\n\n

17. In \u03b2\u207a-decay, a proton changes into:<\/mark><\/strong>
a) Neutron + positron + neutrino
b) Neutron + electron + antineutrino
c) Electron + proton
d) Neutron only
Answer:<\/strong> a) Neutron + positron + neutrino
Explanation:<\/strong> p \u2192 n + e\u207a + \u03bd\u2091.<\/p>\n\n\n\n

18. Which type of radiation does not change the mass number of the nucleus?<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) All of these
Answer:<\/strong> c) \u03b3-rays
Explanation:<\/strong> \u03b3 emission only releases energy, no change in nucleons.<\/p>\n\n\n\n

19. The radioactive isotope used in cancer treatment is:<\/mark><\/strong>
a) C-14
b) Co-60
c) U-238
d) Th-232
Answer:<\/strong> b) Co-60
Explanation:<\/strong> Cobalt-60 emits \u03b3-rays used in radiotherapy.<\/p>\n\n\n\n

20. Half-life of a radioactive substance is:<\/mark><\/strong>
a) Time to complete disintegration
b) Time to reduce activity to zero
c) Time for half the atoms to decay
d) Time for activity to double
Answer:<\/strong> c) Time for half the atoms to decay
Explanation:<\/strong> Half-life = time taken for 50% nuclei to disintegrate.<\/p>\n\n\n\n

21. Radioactive decay is governed by:<\/mark><\/strong>
a) Zero order kinetics
b) First order kinetics
c) Second order kinetics
d) Third order kinetics
Answer:<\/strong> b) First order kinetics
Explanation:<\/strong> Rate of decay \u221d number of nuclei \u2192 first order.<\/p>\n\n\n\n

22. The nucleus of uranium-238 contains:<\/mark><\/strong>
a) 92 protons and 146 neutrons
b) 238 protons
c) 146 protons and 92 neutrons
d) 119 protons and 119 neutrons
Answer:<\/strong> a) 92 protons and 146 neutrons
Explanation:<\/strong> Atomic number (Z) = 92, neutrons = 238 \u2013 92 = 146.<\/p>\n\n\n\n

23. Which isotope is used in radiocarbon dating?<\/mark><\/strong>
a) C-12
b) C-13
c) C-14
d) O-16
Answer:<\/strong> c) C-14
Explanation:<\/strong> C-14 half-life = 5730 years \u2192 used in archaeological dating.<\/p>\n\n\n\n

24. Which radioactive element is used in luminous paints?<\/mark><\/strong>
a) Radium
b) Uranium
c) Thorium
d) Polonium
Answer:<\/strong> a) Radium
Explanation:<\/strong> Radium salts glow in the dark \u2192 used in luminous paints (historically).<\/p>\n\n\n\n

25. The discovery of the nucleus by Rutherford was based on:<\/mark><\/strong>
a) \u03b2-particle scattering
b) \u03b3-ray diffraction
c) \u03b1-particle scattering
d) Neutron bombardment
Answer:<\/strong> c) \u03b1-particle scattering
Explanation:<\/strong> Rutherford\u2019s gold foil experiment with \u03b1-particles revealed the nucleus.<\/p>\n\n\n\n

26. The half-life of C-14 is about:<\/mark><\/strong>
a) 100 years
b) 5730 years
c) 10,000 years
d) 1 million years
Answer:<\/strong> b) 5730 years
Explanation:<\/strong> C-14 has a half-life of 5730 years, useful in archaeology.<\/p>\n\n\n\n

27. If a radioactive element has half-life of 10 days, after 30 days only:<\/mark><\/strong>
a) 1\/2 remains
b) 1\/3 remains
c) 1\/8 remains
d) 1\/16 remains
Answer:<\/strong> c) 1\/8 remains
Explanation:<\/strong> 30 days = 3 half-lives \u2192 (1\/2)\u00b3 = 1\/8.<\/p>\n\n\n\n

28. The activity of a radioactive sample is directly proportional to:<\/mark><\/strong>
a) Time
b) Number of undecayed nuclei
c) Mass of the container
d) Temperature
Answer:<\/strong> b) Number of undecayed nuclei
Explanation:<\/strong> A = \u03bbN, where A = activity, \u03bb = decay constant.<\/p>\n\n\n\n

29. Decay constant (\u03bb) is related to half-life (T\u2081\/\u2082) as:<\/mark><\/strong>
a) \u03bb = T\u2081\/\u2082 \u00d7 log 2
b) \u03bb = ln 2 \/ T\u2081\/\u2082
c) \u03bb = T\u2081\/\u2082 \/ ln 2
d) \u03bb = 1 \/ (2T\u2081\/\u2082)
Answer:<\/strong> b) \u03bb = ln 2 \/ T\u2081\/\u2082
Explanation:<\/strong> Radioactive decay follows first-order kinetics.<\/p>\n\n\n\n

30. If the half-life of a substance is large, its decay constant will be:<\/mark><\/strong>
a) Large
b) Small
c) Zero
d) Infinite
Answer:<\/strong> b) Small
Explanation:<\/strong> \u03bb \u221d 1\/T\u2081\/\u2082 \u2192 large half-life means small decay constant.<\/p>\n\n\n\n

31. Which equation describes radioactive decay?<\/mark><\/strong>
a) N = N\u2080 e^(-\u03bbt)
b) N = N\u2080 e^(\u03bbt)
c) N = N\u2080 \/ (1+\u03bbt)
d) N = N\u2080 \u2013 \u03bbt
Answer:<\/strong> a) N = N\u2080 e^(-\u03bbt)
Explanation:<\/strong> Exponential decay law governs radioactivity.<\/p>\n\n\n\n

32. After two half-lives, the fraction of undecayed atoms is:<\/mark><\/strong>
a) 1\/2
b) 1\/3
c) 1\/4
d) 1\/8
Answer:<\/strong> c) 1\/4
Explanation:<\/strong> (1\/2)\u00b2 = 1\/4.<\/p>\n\n\n\n

33. The unit of half-life is:<\/mark><\/strong>
a) Becquerel
b) Curie
c) Seconds, minutes, years
d) Rutherford
Answer:<\/strong> c) Seconds, minutes, years
Explanation:<\/strong> Half-life is expressed in units of time.<\/p>\n\n\n\n

34. Which isotopes are more stable?<\/mark><\/strong>
a) Even Z \u2013 Even N
b) Odd Z \u2013 Odd N
c) Even Z \u2013 Odd N
d) None
Answer:<\/strong> a) Even Z \u2013 Even N
Explanation:<\/strong> Nuclei with even protons & neutrons are most stable.<\/p>\n\n\n\n

35. Radioactive decay releases mainly:<\/mark><\/strong>
a) Mechanical energy
b) Nuclear binding energy
c) Electrical energy
d) Magnetic energy
Answer:<\/strong> b) Nuclear binding energy
Explanation:<\/strong> Instability \u2192 loss of nuclear binding energy.<\/p>\n\n\n\n

36. Uranium-238 decays finally to form:<\/mark><\/strong>
a) Lead-206
b) Thorium-232
c) Radium-226
d) Bismuth-209
Answer:<\/strong> a) Lead-206
Explanation:<\/strong> U-238 undergoes a decay series ending in Pb-206.<\/p>\n\n\n\n

37. The stable element formed after the decay series of Thorium-232 is:<\/mark><\/strong>
a) Lead-208
b) Lead-206
c) Radium-226
d) Uranium-235
Answer:<\/strong> a) Lead-208
Explanation:<\/strong> Th-232 \u2192 Pb-208 (end product of thorium series).<\/p>\n\n\n\n

38. The isotope used in treatment of thyroid diseases is:<\/mark><\/strong>
a) I-127
b) I-131
c) C-14
d) Co-60
Answer:<\/strong> b) I-131
Explanation:<\/strong> I-131 accumulates in thyroid \u2192 used in diagnosis and treatment.<\/p>\n\n\n\n

39. Which isotope is used in tracer studies of photosynthesis?<\/mark><\/strong>
a) C-12
b) C-13
c) C-14
d) O-16
Answer:<\/strong> c) C-14
Explanation:<\/strong> Radioactive C-14 is used to trace carbon in plants.<\/p>\n\n\n\n

40. Which isotope is used for radiometric dating of rocks?<\/strong><\/mark>
a) C-14
b) U-238
c) K-40
d) Both b and c
Answer:<\/strong> d) Both b and c
Explanation:<\/strong> U-238 and K-40 are used to date rocks and minerals.<\/p>\n\n\n\n

41. The half-life of radon-222 is about:<\/mark><\/strong>
a) 1 year
b) 1600 years
c) 3.8 days
d) 30 years
Answer:<\/strong> c) 3.8 days
Explanation:<\/strong> Radon-222 has short half-life \u2192 radioactive gas.<\/p>\n\n\n\n

42. The isotope used in smoke detectors is:<\/mark><\/strong>
a) Am-241
b) U-235
c) Co-60
d) Th-232
Answer:<\/strong> a) Am-241
Explanation:<\/strong> Americium-241 emits \u03b1-particles \u2192 used in ionization-type smoke detectors.<\/p>\n\n\n\n

43. The half-life of tritium (H-3) is:<\/mark><\/strong>
a) 5730 years
b) 12.3 years
c) 100 years
d) 1 day
Answer:<\/strong> b) 12.3 years
Explanation:<\/strong> Tritium (\u00b3H) has a half-life of ~12.3 years.<\/p>\n\n\n\n

44. Which element has the longest half-life?<\/mark><\/strong>
a) U-235
b) Th-232
c) U-238
d) Pb-206
Answer:<\/strong> b) Th-232
Explanation:<\/strong> Thorium-232 has a half-life of ~1.4 \u00d7 10\u00b9\u2070 years.<\/p>\n\n\n\n

45. The number of disintegrations per second is called:<\/mark><\/strong>
a) Decay constant
b) Half-life
c) Activity
d) Power
Answer:<\/strong> c) Activity
Explanation:<\/strong> Activity A = \u03bbN, measured in Becquerel.<\/p>\n\n\n\n

46. Which radioactive isotope is used in carbon dating?<\/mark><\/strong>
a) C-12
b) C-13
c) C-14
d) O-16
Answer:<\/strong> c) C-14
Explanation:<\/strong> Archaeological dating uses C-14.<\/p>\n\n\n\n

47. Which radioactive isotope is used to study red blood cell circulation?<\/mark><\/strong>
a) Fe-59
b) Co-60
c) I-131
d) C-14
Answer:<\/strong> a) Fe-59
Explanation:<\/strong> Iron-59 is used to trace blood circulation.<\/p>\n\n\n\n

48. Which of the following isotopes is used in agriculture to study phosphorus uptake?<\/strong><\/mark>
a) P-32
b) S-35
c) C-14
d) I-131
Answer:<\/strong> a) P-32
Explanation:<\/strong> Phosphorus-32 is used in tracer studies in plants.<\/p>\n\n\n\n

49. Which is used in sterilization of medical instruments?<\/mark><\/strong>
a) \u03b2-rays
b) \u03b3-rays (Co-60)
c) \u03b1-rays
d) Neutrons
Answer:<\/strong> b) \u03b3-rays (Co-60)
Explanation:<\/strong> Gamma irradiation sterilizes surgical instruments.<\/p>\n\n\n\n

50. The main reason for nuclear stability is:<\/mark><\/strong>
a) Balance of protons and neutrons
b) Electrons in orbit
c) High atomic weight
d) High density
Answer:<\/strong> a) Balance of protons and neutrons
Explanation:<\/strong> Stability depends on neutron-to-proton (N\/Z) ratio.<\/p>\n\n\n\n

51. A nuclear reaction is a change that occurs in:<\/mark><\/strong>
a) Electrons
b) Atomic nucleus
c) Orbitals
d) Molecules
Answer:<\/strong> b) Atomic nucleus
Explanation:<\/strong> Nuclear reactions involve changes in the composition of nuclei.<\/p>\n\n\n\n

52. In a nuclear fission reaction, a heavy nucleus splits into:<\/mark><\/strong>
a) Lighter nuclei
b) Neutrons only
c) Protons only
d) Electrons
Answer:<\/strong> a) Lighter nuclei
Explanation:<\/strong> Fission splits a heavy nucleus (like U-235) into two medium nuclei plus neutrons and energy.<\/p>\n\n\n\n

53. Which of the following is used as fuel in nuclear reactors?<\/mark><\/strong>
a) U-235
b) Th-232
c) Pu-239
d) All of these
Answer:<\/strong> d) All of these
Explanation:<\/strong> Uranium-235, Thorium-232, and Plutonium-239 are nuclear fuels.<\/p>\n\n\n\n

54. Which particle initiates nuclear fission?<\/mark><\/strong>
a) Proton
b) Neutron
c) \u03b1-particle
d) Electron
Answer:<\/strong> b) Neutron
Explanation:<\/strong> A neutron is used because it has no charge and can easily enter the nucleus.<\/p>\n\n\n\n

55. Which isotope is most commonly used in nuclear power plants?<\/mark><\/strong>
a) U-235
b) U-238
c) Th-232
d) C-14
Answer:<\/strong> a) U-235
Explanation:<\/strong> Uranium-235 undergoes controlled fission in nuclear reactors.<\/p>\n\n\n\n

56. In a nuclear chain reaction, neutrons released cause:<\/mark><\/strong>
a) Cooling of reactor
b) Further fission reactions
c) Reduction in energy
d) Production of \u03b3-rays only
Answer:<\/strong> b) Further fission reactions
Explanation:<\/strong> Each fission releases neutrons \u2192 sustains chain reaction.<\/p>\n\n\n\n

57. The moderator used in nuclear reactors is:<\/mark><\/strong>
a) Graphite or Heavy water
b) Lead
c) Mercury
d) Sodium
Answer:<\/strong> a) Graphite or Heavy water
Explanation:<\/strong> Moderators slow down fast neutrons for sustained fission.<\/p>\n\n\n\n

58. Which of the following is used as a coolant in nuclear reactors?<\/mark><\/strong>
a) Graphite
b) Sodium or Heavy water
c) Zinc
d) Lead oxide
Answer:<\/strong> b) Sodium or Heavy water
Explanation:<\/strong> Liquid sodium or heavy water removes heat from the reactor.<\/p>\n\n\n\n

59. Control rods in nuclear reactors are made of:<\/mark><\/strong>
a) Aluminium
b) Cadmium or Boron
c) Iron
d) Lead
Answer:<\/strong> b) Cadmium or Boron
Explanation:<\/strong> These absorb excess neutrons to control the chain reaction.<\/p>\n\n\n\n

60. Nuclear fusion is the process where:<\/strong><\/mark>
a) Heavy nuclei split
b) Light nuclei combine
c) Neutrons are absorbed
d) Electrons are emitted
Answer:<\/strong> b) Light nuclei combine
Explanation:<\/strong> Fusion combines light nuclei (like H isotopes) into heavier nuclei with huge energy release.<\/p>\n\n\n\n

61. Energy produced in stars, including the Sun, comes from:<\/mark><\/strong>
a) Fission
b) Fusion of hydrogen nuclei
c) Radioactive decay
d) Combustion
Answer:<\/strong> b) Fusion of hydrogen nuclei
Explanation:<\/strong> Stars fuse hydrogen \u2192 helium, releasing massive energy.<\/p>\n\n\n\n

62. Which isotopes of hydrogen are used in nuclear fusion?<\/mark><\/strong>
a) Protium and Deuterium
b) Deuterium and Tritium
c) Protium and Tritium
d) Only Protium
Answer:<\/strong> b) Deuterium and Tritium
Explanation:<\/strong> D + T \u2192 He + neutron + huge energy.<\/p>\n\n\n\n

63. Which reaction has higher energy output?<\/mark><\/strong>
a) Nuclear fission
b) Nuclear fusion
c) Chemical combustion
d) Electrolysis
Answer:<\/strong> b) Nuclear fusion
Explanation:<\/strong> Fusion releases more energy per nucleon than fission.<\/p>\n\n\n\n

64. The hydrogen bomb is based on:<\/mark><\/strong>
a) Nuclear fission
b) Nuclear fusion
c) Both fission and fusion
d) Chemical explosion
Answer:<\/strong> c) Both fission and fusion
Explanation:<\/strong> Fission triggers the extremely high temperature needed for fusion.<\/p>\n\n\n\n

65. The atomic bomb dropped on Hiroshima (1945) used:<\/mark><\/strong>
a) U-235
b) Pu-239
c) Th-232
d) C-14
Answer:<\/strong> a) U-235
Explanation:<\/strong> \u201cLittle Boy\u201d bomb used U-235.<\/p>\n\n\n\n

66. The atomic bomb dropped on Nagasaki (1945) used:<\/mark><\/strong>
a) U-235
b) Pu-239
c) Th-232
d) Co-60
Answer:<\/strong> b) Pu-239
Explanation:<\/strong> \u201cFat Man\u201d bomb used Pu-239.<\/p>\n\n\n\n

67. The peaceful use of nuclear energy is in:<\/mark><\/strong>
a) Nuclear weapons
b) Nuclear power plants
c) Bomb testing
d) Radiation hazards
Answer:<\/strong> b) Nuclear power plants
Explanation:<\/strong> Controlled fission generates electricity.<\/p>\n\n\n\n

68. Which of the following is a fusion reaction?<\/mark><\/strong>
a) \u00b2H + \u00b3H \u2192 \u2074He + n
b) \u00b2\u00b3\u2075U + n \u2192 fission products
c) \u00b2\u00b3\u2078U \u2192 \u00b2\u00b3\u2074Th + \u03b1
d) \u2076\u2070Co \u2192 \u2076\u2070Ni + \u03b3
Answer:<\/strong> a) \u00b2H + \u00b3H \u2192 \u2074He + n
Explanation:<\/strong> Deuterium + Tritium fusion reaction.<\/p>\n\n\n\n

69. Which radioactive isotope is used as a fuel in breeder reactors?<\/strong><\/mark>
a) U-235
b) U-238
c) Th-232
d) Both b and c
Answer:<\/strong> d) Both b and c
Explanation:<\/strong> U-238 and Th-232 convert into fissile Pu-239 and U-233 in breeder reactors.<\/p>\n\n\n\n

70. The first nuclear reactor in India was:<\/mark><\/strong>
a) CIRUS
b) Dhruva
c) Apsara
d) Kamini
Answer:<\/strong> c) Apsara
Explanation:<\/strong> Apsara, set up in 1956 at Trombay, was India\u2019s first reactor.<\/p>\n\n\n\n

71. Which Indian nuclear power station is the largest?<\/mark><\/strong>
a) Tarapur
b) Kaiga
c) Kudankulam
d) Kalpakkam
Answer:<\/strong> c) Kudankulam
Explanation:<\/strong> Kudankulam (Tamil Nadu) is India\u2019s largest nuclear power station.<\/p>\n\n\n\n

72. The energy produced in nuclear reactions comes from:<\/mark><\/strong>
a) Conversion of electrons
b) Mass-energy equivalence (E=mc\u00b2)
c) Movement of neutrons
d) Nuclear force only
Answer:<\/strong> b) Mass-energy equivalence (E=mc\u00b2)
Explanation:<\/strong> Loss of mass in reactions converts to energy.<\/p>\n\n\n\n

73. Which radioactive isotope is used in pacemakers?<\/mark><\/strong>
a) U-235
b) Pu-239
c) Co-60
d) Pu-238
Answer:<\/strong> d) Pu-238
Explanation:<\/strong> Plutonium-238 provides long-lasting power in heart pacemakers.<\/p>\n\n\n\n

74. The critical mass in a fission reaction is:<\/mark><\/strong>
a) Minimum mass of fuel required to sustain chain reaction
b) Maximum fuel mass
c) Zero
d) Amount of fuel that stops reaction
Answer:<\/strong> a) Minimum mass of fuel required to sustain chain reaction
Explanation:<\/strong> Critical mass ensures enough neutrons for continuous fission.<\/p>\n\n\n\n

75. The coolant used in fast breeder reactors is:<\/mark><\/strong>
a) Water
b) Sodium metal
c) Mercury
d) Heavy water
Answer:<\/strong> b) Sodium metal
Explanation:<\/strong> Fast breeder reactors use liquid sodium as coolant due to excellent heat transfer.<\/p>\n\n\n\n

76. The harmful effect of \u03b1-particles is mainly due to:<\/mark><\/strong>
a) High penetration
b) High ionization power
c) High speed
d) Low energy
Answer:<\/strong> b) High ionization power
Explanation:<\/strong> \u03b1-particles have low penetration but strong ionization, damaging tissues if ingested or inhaled.<\/p>\n\n\n\n

77. \u03b2-particles cause damage because they:<\/mark><\/strong>
a) Are heavy particles
b) Have moderate penetration and ionizing power
c) Have no charge
d) Do not interact with matter
Answer:<\/strong> b) Have moderate penetration and ionizing power
Explanation:<\/strong> \u03b2-rays penetrate skin and damage living tissues.<\/p>\n\n\n\n

78. \u03b3-rays are dangerous because:<\/mark><\/strong>
a) They are positively charged
b) They have very high penetration power
c) They are heavy particles
d) They do not interact with tissues
Answer:<\/strong> b) They have very high penetration power
Explanation:<\/strong> \u03b3-rays penetrate deeply, causing severe internal damage.<\/p>\n\n\n\n

79. Which unit measures the biological effect of radiation?<\/mark><\/strong>
a) Becquerel
b) Curie
c) Sievert
d) Hertz
Answer:<\/strong> c) Sievert
Explanation:<\/strong> Sievert (Sv) measures dose equivalent (biological effect).<\/p>\n\n\n\n

80. The device used to detect and measure radiation is:<\/mark><\/strong>
a) Ammeter
b) Voltmeter
c) Geiger-M\u00fcller counter
d) Galvanometer
Answer:<\/strong> c) Geiger-M\u00fcller counter
Explanation:<\/strong> GM counter detects \u03b1, \u03b2, \u03b3 radiation by ionization of gas.<\/p>\n\n\n\n

81. Which device uses photographic film to measure radiation exposure?<\/mark><\/strong>
a) Scintillation counter
b) Dosimeter
c) GM counter
d) Potentiometer
Answer:<\/strong> b) Dosimeter
Explanation:<\/strong> Film badges (dosimeters) record accumulated radiation exposure of workers.<\/p>\n\n\n\n

82. Which radiation detector uses flashes of light?<\/mark><\/strong>
a) Scintillation counter
b) GM counter
c) Dosimeter
d) Electroscope
Answer:<\/strong> a) Scintillation counter
Explanation:<\/strong> Scintillations (flashes) occur when radiation hits a fluorescent screen.<\/p>\n\n\n\n

83. The harmful effects of radiation depend on:<\/mark><\/strong>
a) Type of radiation
b) Dose received
c) Duration of exposure
d) All of the above
Answer:<\/strong> d) All of the above
Explanation:<\/strong> All factors contribute to radiation damage.<\/p>\n\n\n\n

84. Acute radiation syndrome occurs due to:<\/mark><\/strong>
a) Small exposure
b) High radiation dose in short time
c) Long exposure to low dose
d) Only \u03b1-rays
Answer:<\/strong> b) High radiation dose in short time
Explanation:<\/strong> Acute high exposure damages tissues severely.<\/p>\n\n\n\n

85. Which cells are most sensitive to radiation?<\/mark><\/strong>
a) Brain cells
b) Nerve cells
c) Reproductive cells and bone marrow
d) Muscle cells
Answer:<\/strong> c) Reproductive cells and bone marrow
Explanation:<\/strong> Rapidly dividing cells are most radiation-sensitive.<\/p>\n\n\n\n

86. Which radioactive gas causes lung cancer?<\/mark><\/strong>
a) Radon
b) Argon
c) Krypton
d) Neon
Answer:<\/strong> a) Radon
Explanation:<\/strong> Radon gas accumulates in basements \u2192 lung cancer risk.<\/p>\n\n\n\n

87. Which of the following is a man-made radiation hazard?<\/mark><\/strong>
a) Cosmic rays
b) Radon gas
c) X-rays
d) Solar radiation
Answer:<\/strong> c) X-rays
Explanation:<\/strong> X-rays are artificially produced ionizing radiation.<\/p>\n\n\n\n

88. The safe limit of radiation for humans per year is about:<\/mark><\/strong>
a) 1 Sievert
b) 100 Sieverts
c) 1 milliSievert
d) 20 milliSieverts
Answer:<\/strong> d) 20 milliSieverts
Explanation:<\/strong> Recommended occupational dose limit \u2248 20 mSv\/year.<\/p>\n\n\n\n

89. The effect of long-term low radiation exposure is called:<\/mark><\/strong>
a) Acute radiation syndrome
b) Chronic radiation effect
c) Radiation shock
d) None
Answer:<\/strong> b) Chronic radiation effect
Explanation:<\/strong> Long-term exposure \u2192 cancer, genetic effects.<\/p>\n\n\n\n

90. The isotope used in radiotherapy for cancer is:<\/mark><\/strong>
a) Co-60
b) C-14
c) I-131
d) U-235
Answer:<\/strong> a) Co-60
Explanation:<\/strong> Cobalt-60 emits \u03b3-rays used in cancer treatment.<\/p>\n\n\n\n

91. The isotope used in PET (Positron Emission Tomography) scans is:<\/mark><\/strong>
a) C-14
b) F-18
c) Co-60
d) U-235
Answer:<\/strong> b) F-18
Explanation:<\/strong> Fluorine-18 is used in PET imaging.<\/p>\n\n\n\n

92. Which isotope is used to detect blood clots?<\/mark><\/strong>
a) I-131
b) Na-24
c) Xe-133
d) Co-60
Answer:<\/strong> b) Na-24
Explanation:<\/strong> Sodium-24 is used as a tracer in blood circulation studies.<\/p>\n\n\n\n

93. Radiation used to sterilize medical instruments:<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) Neutrons
Answer:<\/strong> c) \u03b3-rays
Explanation:<\/strong> Gamma irradiation sterilizes without heat.<\/p>\n\n\n\n

94. Which law states that radioactivity decreases exponentially with time?<\/mark><\/strong>
a) Newton\u2019s law
b) First order kinetics law
c) Radioactive decay law
d) Avogadro\u2019s law
Answer:<\/strong> c) Radioactive decay law
Explanation:<\/strong> N = N\u2080e^(-\u03bbt).<\/p>\n\n\n\n

95. The binding energy of a nucleus explains:<\/mark><\/strong>
a) Nuclear stability
b) Atomic size
c) Electron affinity
d) Ionization energy
Answer:<\/strong> a) Nuclear stability
Explanation:<\/strong> Higher binding energy per nucleon = more stable nucleus.<\/p>\n\n\n\n

96. Radiation causes genetic damage by:<\/mark><\/strong>
a) Ionization of DNA molecules
b) Heating the body
c) Increasing cell growth
d) Strengthening tissues
Answer:<\/strong> a) Ionization of DNA molecules
Explanation:<\/strong> Ionizing radiation alters DNA \u2192 mutations.<\/p>\n\n\n\n

97. Which radiation is deflected by electric and magnetic fields?<\/mark><\/strong>
a) \u03b1 and \u03b2
b) \u03b3 only
c) Neutrons
d) All of the above
Answer:<\/strong> a) \u03b1 and \u03b2
Explanation:<\/strong> \u03b1 (+ charge) and \u03b2 (\u2013 charge) are deflected; \u03b3 and neutrons are neutral.<\/p>\n\n\n\n

98. Which nuclear radiation is most suitable for thickness measurement in industries?<\/mark><\/strong>
a) \u03b1-rays
b) \u03b2-rays
c) \u03b3-rays
d) X-rays
Answer:<\/strong> b) \u03b2-rays
Explanation:<\/strong> Beta radiation is used to monitor thickness of sheets in industries.<\/p>\n\n\n\n

99. The term “radioisotope” refers to:<\/mark><\/strong>
a) A stable isotope
b) A radioactive isotope
c) A mixture of isotopes
d) A tracer only
Answer:<\/strong> b) A radioactive isotope
Explanation:<\/strong> Radioisotopes are unstable isotopes emitting radiation.<\/p>\n\n\n\n

100. Which principle of Einstein explains nuclear energy?<\/mark><\/strong>
a) E = mc\u00b2
b) E = hf
c) PV = nRT
d) F = ma
Answer:<\/strong> a) E = mc\u00b2
Explanation:<\/strong> Mass defect converts into energy during nuclear reactions.<\/p>\n","protected":false},"excerpt":{"rendered":"

1. Radioactivity was discovered by:a) Marie Curieb) Henri Becquerelc) Rutherfordd) J.J. ThomsonAnswer: b) Henri BecquerelExplanation: In 1896, Henri Becquerel discovered radioactivity while working with uranium salts. 2. Marie Curie discovered which radioactive elements?a) Uranium and Thoriumb) Polonium and Radiumc) Uranium and Radiumd) Thorium and RadonAnswer: b) Polonium and RadiumExplanation: Marie and Pierre Curie discovered polonium<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,1],"tags":[15794,15798,15797,15886,15892,15876,15898,15901,15887,15899,15879,15883,15759,15753,15757,16040,4029,15897,5649,5623,16039,15800,15749,15893,15900,15805,15801,15796,15795,16041,15802,10959,15896,15894],"class_list":{"0":"post-12782","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-chemistry","7":"category-blog","8":"tag-alpha-decay","9":"tag-atomic-nucleus","10":"tag-beta-decay","11":"tag-chemistry-formulas","12":"tag-chemistry-learning","13":"tag-chemistry-mcqs","14":"tag-chemistry-preparation-material","15":"tag-chemistry-questions-and-answers","16":"tag-chemistry-quiz","17":"tag-chemistry-revision","18":"tag-chemistry-study-material","19":"tag-competitive-exam-chemistry","20":"tag-decay-constant","21":"tag-gamma-radiation","22":"tag-half-life","23":"tag-isotopes","24":"tag-mcqs-adda","25":"tag-mcqs-for-chemistry-exam","26":"tag-mcqs-for-pc-psi-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","27":"tag-mcqs-for-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","28":"tag-nuclear-chemistry","29":"tag-nuclear-energy","30":"tag-nuclear-reactions","31":"tag-physics-and-chemistry-concepts","32":"tag-psc-chemistry-mcqs","33":"tag-radiation-measurement","34":"tag-radiation-safety","35":"tag-radioactive-applications","36":"tag-radioactive-elements","37":"tag-radioactivity-in-chemistry","38":"tag-radioactivity-problems","39":"tag-radioactivity-top-100-mcqs-with-answer-and-explanation","40":"tag-ssc-chemistry-mcqs","41":"tag-upsc-chemistry-mcqs"},"_links":{"self":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12782","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/comments?post=12782"}],"version-history":[{"count":3,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12782\/revisions"}],"predecessor-version":[{"id":12945,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12782\/revisions\/12945"}],"wp:attachment":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/media?parent=12782"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/categories?post=12782"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/tags?post=12782"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}