# Class 12 Physics Chapter 13 Nuclei MCQ Questions with Answers

Nuclei Class 12 MCQ is one of the best strategies to prepare for the CBSE Class 12 Board exam. If you want to complete a grasp concept or work on one’s score, there is no method except constant practice. Students can improve their speed and accuracy by doing more MCQs on Nuclei Class 12, which will help them all through their board test.

## Nuclei Class 12 MCQ Questions with Answers

Class 12 Physics MCQ with answers are given here to chapter the Nuclei. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Physics syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Class 12 Nuclei MCQ with answers pdf free download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving CBSE Class 12 Nuclei MCQ with answers given below.

Question 1. If the radioactive decay constant of radium is 1.07 × 10–4 per year. Then its half life period approximately is equal to:
(a) 5000 years
(b) 6500 years
(c) 7000 years
(d) 8900 years

B

Question 2. In 88Ra226 nucleus there are :
(a) 226 protons and 88 electrons
(b) 138 protons and 88 neutrons
(c) 226 neutrons and 138 electrons
(d) 138 neutrons and 88 protons

D

Question 3. In the nuclear reaction, there is a conservation of:
(a) momentum
(b) mass
(c) energy
(d) all of these

A

Question 4. The activity of radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes, the decay constant is approximately :
(a) 0.922 per minute
(b) 0.270 per minute
(c) 0.461 per minute
(d) 0.39 per minute

C

Question 5. The activity of a radioactive sample is 1.6 curie and its half life is 2.5 days. Then activity after 10 days will be :
(a) 0.16 curie
(b) 0.8 curie
(c) 0.1 curie
(d) 0.4 curie

C

Question 6. The reaction responsible for the production of light energy from the sun will be:
(a) fission
(b) fusion
(c) nuclear
(d) none of these

B

Question 7. Which one of the following is used as a moderator in nuclear reaction ?
(a) Uranium
(b) Heavy water
(d) Plutonium

B

Question 8. Half life of a substance is 20 minutes, then the time between 33 % decay and 67 % decay will be
(a) 20 minute
(b) 40 minute
(c) 50 minute
(d) 10 minute

A

Question 9. Consider the following nuclear reaction X200 → A110 + B90 + Energy
If the binding energy per nucleon for X, A and B are 7.4 MeV, and 8.2 MeV and 8.2 MeV respectively, the energy released will be :
(a) 90 MeV
(b) 110 MeV
(c) 200 MeV
(d) 160 MeV

D

Question 10. The function of heavy water in a nuclear reactor to
(a) slow down the neutrons
(b) increase the neutrons
(c) stop the electrons
(d) none of these

A

Question 11. In each fission of 92U235 releases 200 MeV, how many fissions must occur per second to produce power of 1 kW ?
(a) 1.25 × 1018
(b) 3.125 × 1013
(c) 3.2 × 1018
(d) 1.25 × 1013

B

Question 12. Which one of the following has the highest neutrons ratio ?
(a) 92U235
(b) 8O16
(c) 2He4
(d) 26Fe56

A

Question 13. When radioactive substance emits an a-particle, then its position in the periodic table is lowered by
(a) two places
(b) three places
(c) five places
(c) one place

A

Question 14. A radioactive substance decays to 1/16th of its initial activity in 40 days. The half-life of the radioactive substance expressed in days is
(a) 2.5
(b) 5
(c) 10
(d) 20

C

Question 15. In an atom bomb, the energy is released because of the :
(a) chain reaction of neutrons and 92U238
(b) chain reaction of neutrons and 92U235
(c) chain reaction of neutrons and 92U236
(d) chain reaction of neutrons and 92U240

B

Question 16. Nuclear fusion is possible
(a) only between light nuclei
(b) only between heavy nuclei
(c) between both light and heavy nuclei
(d) only between nuclei which are stable against b-decay

A

Question 17. In a material medium, when a positron meets an electron both the particles annihilate leading to the emission of two gamma ray photons. This process forms the basis of an important diagnostic procedure called
(a) MRI
(b) PET
(c) CAT
(d) SPECT

B

Question 18. Carbon dating is best suited for determining the age of fossils if their age in years is of the order of
(a) 103
(b) 104
(c) 105
(d) 106

B

Question 19. Radioactive nuclei that are injected into a potient collected at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tools called
(a) Gamma camera
(b) CAT can
(d) Gamma ray spectroscopy

C

Question 20. When an electron-positron pair annihilates, the energy released is about
(a) 0.8 × 10–13 J
(b) 1.6 × 10–13 J
(c) 3.2 × 10–13 J
(d) 4.8 × 10–13 J

B

Question 21. A radioactive material has half-life of 10 days.What fraction of the material would remain after 30 days ?
(a) 0.5
(b) 0.25
(c) 0.125
(d) 0.33

C

Question 22. 238U has 92 protons and 238 nucleons. It decays by emitting an Alpha particle and becomes
(a) 23492U
(b) 234 90Th
(c) 23592U
(d) 23793Np

B

Question 23. The operation of a nuclear reactor is said to be critical, if the multiplication factor (K) has a value
(a) 1
(b) 1.5
(c) 2.1
(d) 2.5

A

Question 24. If Alpha, Beta and Gamma rays carry same momentum, which has the longest wavelength
(a) Alpha rays
(b) Beta rays
(c) Gamma rays
(d) None, all have some wavelength

D

Question 25. Calculate power output of 23592U reactor, if it takes 30 days to use up 2 kg of fuel, and if each fission gives 185 MeV of useable energy. Avogadro’s number = 6 × 1023 /mol?
(a) 56.3 MW
(b) 60.3 MW
(c) 58.3 MW
(d) 54.3 MW

C

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Question 26. Starting with a sample of pure 66Cu,7/8 of it decays into Zn in 15 minutes. The corresponding half life is
(a) 15 minutes
(b) 10 minutes
(c) 7 .1/2  minutes
(d) 5 minutes

D

Question 27. What is the amount of energy released by deuterium and tritium fusion?
(a) 60.6 eV
(b) 123.6 eV
(c) 17.6 eV
(d) 28.3 eV

C

Question 28. A radioactive material decays by simultaneous emission of two particles with respective halflives 1620 and 810 years. The time, in years, after which one-fourth of the material reamins is
(a) 1080
(b) 2430
(c) 3240
(d) 4860

A

Question 29. If the binding energy per nucleon of a nuclide is high then
(a) It should be abundantly available in nature
(b) It will decay instantly
(c) It will have a large disintegration constant
(d) It will have a small half-life.

A

Question 30. The half life of a radioactive substance against a -decay is 1.2 × 107 s. What is the decay rate for 4.0 × 1015 atoms of the substance
(a) 4.6 × 10 12 atoms/s
(b) 2.3 × 10 11 atoms/s
(c) 4.6 × 10 10 atoms/s
(d) 2.3 × 10 atoms/s

D

Question 31. Activity of a radioactive sample decreases to (l/3)rd of its original value in 3 days. Then, in 9 days its activity will become
(a) (1/27) of the original value
(b) (1/9) of the original value
(c) (1/18) of the original value
(d) (1/3) of the original value

A

Question 32. Actinium 231, 231Ac89, emit in succession two b-particles, four alphas, one b and one alpha plus several g rays. What is the resultant isotope:
(a) 221 Au79
(b) 211 Au 79
(c) 221 Pb 82
(d) 211 Pb 82

D

Question 33. The fossil bone has a 14C : 12C ratio, which is [1/16] of that in a living animal bone. If the halflife of 14C is 5730 years, then the age of the fossil bone is
(a) 11460 years
(b) 17190 years
(c) 22920 years
(d) 45840 years

C

Question 34. Which one of the following pairs of nuclei are isotones?
(a) 34Se74, 31Ga71
(b) 38Sr84, 38Sr86
(c) 42Mo92, 40Zr92
(d) 20Ca40, 16S32

A

Question 35. An archaeologist analyses the wood in a prehistoric structure and finds that C14 (Half life = 5700 years) to C12 is only one-fourth of that found in the cells of buried plants. The age of the wood is about
(a) 5700 years
(b) 2850 years
(c) 11,400 years
(d) 22,800 years

C

Question 36. A nucleus represented by the symbol Z AX has
(a) Z neutrons and A – Z protons
(b) Z protons and A – Z neutrons
(c) Z protons and A neutrons
(d) A protons and Z – A neutrons

B

Question 37. The mass number of a nucleus is
(a) always less than its atomic number
(b) always more than its atomic number
(c) sometimes equal to its atomic number
(d) sometimes less than and sometimes more than its atomic number

C

Question 38. The constituents of atomic nuclei are believed to be
(a) neutrons and protons
(b) protons only
(c) electrons and protons
(d) electrons, protons and neutrons

A

Question 39. Atomic weight of Boron is 10.81 and it has two isotopes 5B10 and 5B11. Then the ratio of 5B10 : 5B11 in nature would be
(a) 15 : 16
(b) 10 : 11
(c) 19 : 81
(d) 81 : 19

C

Question 40. In the nucleus of 11Na23, the number of protons, neutrons and electrons are
(a) 11, 12, 0
(b) 23, 12, 11
(c) 12, 11, 0
(d) 23, 11, 12

A

Question 41. A neutron travelling with a velocity v and kinetic energy E has a perfectly elastic head-on collision with a nucleus of an atom of mass number A at rest. The fraction of total energy retained by the neutron is approximately
(a) [(A – 1)/(A + 1)]2
(b) [(A + 1)/(A – 1)]2
(c) [(A – 1)/A]2
(d) [(A + 1)/A]2

A

Question 42. The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 & 975 counts per minute at T = 5 minutes. The decay constant is approximately.
(a) 0.922 per minutes
(b) 0.691 per minutes
(c) 0.461 per minutes
(d) 0.230 per minutes

C

Question 43. Atomic weight of boron is 10.81 and it has two isotopes 5B10 and 5B11. Then ratio of 5B10 : 5B11 in nature would be
(a) 19 : 81
(b) 10 : 11
(c) 15 : 16
(d) 81 : 19

A

Question 44. If the radius of a nucleus 256X is 8 fermi, then the radius of 4He nucleus will be
(a) 16 fermi
(b) 2 fermi
(c) 32 fermi
(d) 4 fermi

B

Question 45. Which of the following statements is true?
(a) 78Pt192 has 78 neutrons
(b) 84Po214 → 82Pb210 + β
(c) 92U238 → 90Th234 + 2He4
(d) 90Th234 → 91Pa234 + 2He4

C

Question 46. The energy released per fission of a 92U235 nucleus is nearly
(a) 200 eV
(b) 20 eV
(c) 200 MeV
(d) 2000 eV

C

Question 47. Consider a radioactive material of half-life 1.0 minute. If one
of the nuclei decays now, the next one will decay
(a) after 1 minute
(b) after (1/loge2)  minute
(c) after 1/N minute, where N is the number of nuclei present at that moment
(d) after any time

D

Question 48. Order of magnitude of density of uranium nucleus is (mp = 1.67 × 10–27 kg)
(a) 1020 kg / m3
(b) 1017 kg / m3
(c) 1014 kg / m3
(d) 1011 kg / m3

B

Question 49. The masses of neutron and proton are 1.0087 a.m.u. and 1.0073 a.m.u. respectively. If the neutrons and protons combine to form a helium nucleus (alpha particles) of mass 4.0015 a.m.u the binding energy fo the helium nucleus will be (1 a.m.u. = 931 MeV)
(a) 28.4 MeV
(b) 20.8 MeV
(c) 27.3 MeV
(d) 14.2 MeV

A

Question 50. Half lives of two radio active substance A & B are respectively 20 minutes & 40 minutes. Initially the samples of A & B have equal numbers of nulcei. After 80 minutes the ratio of remaining numbers of A & B nuclei is
(a) 1 : 16
(b) 4 : 1
(c) 1 : 4
(d) 1 : 1

C

Question 51. At any instant, the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances ?
(a) 1 : 1
(b) 2 : 1
(c) 1 : 2
(d) 1 : 4

A

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