Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Nuclei with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

Chapter 13 Nuclei MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Nuclei provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. During a mean life of a radioactive element the fraction that disintegrates is:

Question. The gravitational force between a H-atom and another particle of mass m will be given by Newton’s law:

Question. When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom
(a) do not change for any type of radioactivity.
(b) change for a and β radioactivity but not for g-radioactivity.
(c) change for a-radioactivity but not for others.
(d) change for β-radioactivity but not for others.

Question. A nuclear reaction is given below. The masses in amu of reactant and product nuclei are given in brackets:

The value of energy Q is
(a) 1.234 MeV
(b) 0.91 MeV
(c) 0.465 MeV
(d) 1.862 MeV

Question. When boron (¹⁰₅B ) is bombarded by neutron, alpha-particles is emitted. The resulting nucleushas the mass number
(a) 11
(b) 7
(c) 6
(d) 15

Question. The binding energies per nucleon of deuteron (₁H²) and helium (₂He⁴) nuclei are 1.1 MeV and 7 MeV respectively. If two deuterons fuse together to form a helium nucleus, then energy produced is:
(a) 5.9 MeV
(b) 23.6 MeV
(c) 26.9 MeV
(d) 32.4 MeV

Question. M_x and M_y denote the atomic masses of the parent and the daughter nuclei respectively in a radioactive decay. The Q-value for a β^– decay is Q₁ and that for a β⁺ decay is Q₂. If me denotes the mass of an electron, then which of the following statements is correct?
(a) Q₁ = (M_x – M_y) c² = and Q₂ = (M_x – M_y – 2m_e)c²
(b) Q₁ = (M_x – M_y)c² and Q₂ = (M_x – M_y )c²
(c) Q₁ = (M_x – M_y – 2 m_e) c² and Q₂ = (M_x – M_y +2 m_e)c²
(d) Q₁ = (M_x – M_y + 2 m_e) c² and Q₂ = (M_x – M_y +2 m_e)c²

Question. How much energy will approximately be released if all the atoms of 1 kg of deuterium could undergo fusion? [Assume energy released per deuterium nucleus is 2 MeV]
(a) 2 × 10⁷ kWh
(b) 9 × 10¹³ J
(c) 6 × 10²⁷ calorie
(d) 9 × 10¹³ MeV

Question. The half life of ²¹⁵ At is 100 μs. The time taken for the activity of the sample of ²¹⁵ At to decay to 1/16
th of its initial value is
(a) 400 μs
(b) 300 μs
(c) 40 μs
(d) 6.3 μs

Question. Samples of two radioactive nuclides A and B are taken. λ_A and λ_B are the disintegration constants of A and B respectively. In which of the following cases, the two samples can simultaneously have the same decay rate at any time?
(a) Initial rate of decay of A is twice the initial rate of decay of B and λ_A = λ_B.
(b) Initial rate of decay of A is twice the initial rate of decay of B and λ_A > λ_B.
(c) Initial rate of decay of B is twice the initial rate of decay of A and λ_A > λ_B.
(d) Initial rate of decay of B is same as the rate of decay of A at t = 2h and λ_B < λ_A.

Question. For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is
(a) 20
(b) 10
(c) 30
(d) 15

Question. Heavy stable nuclei have more neutrons than protons. This is because of the fact that
(a) neutrons are heavier than protons.
(b) electrostatic force between protons are repulsive.
(c) neutrons decay into protons through beta decay.
(d) nuclear forces between neutrons are weaker than that between protons.

Question. When an a-particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as
(a) 1/m²
(b) m
(c) 1/m
(d) 1/√m

Question. In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderator used have light nuclei. Heavy nuclei will not serve the purpose because
(a) they will break up.
(b) elastic collision of neutrons with heavy nuclei will not slow them down.
(c) the net weight of the reactor would be unbearably high.
(d) substances with heavy nuclei do not occur in liquid or gaseous state at room temperature.

Question. The binding energy per nucleon in ₃⁷Li and ₂⁴He are 7.06 MeV and 5.60 MeV respectively, then in the reaction: p + ⁷₃ Li → 2 (₂⁴He) the energy of proton must be:
(a) 28.24 MeV
(b) 17.28 MeV
(c) 1.46 MeV
(d) 39.2 MeV

Question. Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material with a half life of 1 year. After 1 year,
(a) all the containers will have 5000 atoms of the material.
(b) all the containers will contain the same number of atoms of the material but that number will only be approximately 5000.
(c) the containers will in general have different numbers of the atoms of the material but their average will be close to 5000.
(d) none of the containers can have more than 5000 atoms.

Question. The variation of decay rate of two radioactive samples A and B with time is shown in figure. Which of the following statements are true?
(a) Decay constant of A is greater than that of B, hence A always decays faster than B.
(b) Decay constant of B is greater than that of A but its decay rate is always smaller than that of A.
(c) Decay constant of A is greater than that of B but it does not always decay faster than B.
(d) Decay constant of B is smaller than that of A but still its decay rate becomes equal to that of A at a later instant.

Question. Tritium is an isotope of hydrogen whose nucleus Triton contains 2 neutrons and 1 proton. Free neutrons decay into p+er+vr . If one of the neutrons in Triton decays, it would transform into He³ nucleus. This does not happen. This is because
(a) Triton energy is less than that of a He³ nucleus.
(b) the electron created in the beta decay process cannot remain in the nucleus.
(c) both the neutrons in triton have to decay simultaneously resulting in a nucleus with 3 protons, which is not a He³ nucleus.
(d) because free neutrons decay due to external perturbations which is absent in a triton nucleus.

Question. In gamma ray emission from a nucleus
(a) only the proton number changes
(b) both the neutron number and the proton number change
(c) there is no change in the proton number and the neutron number
(d) only the neutron number changes

Question. A radioactive substance has a half life of four months. Three fourth of the substance will decay in
(a) three months
(b) four months
(c) eight months
(d) twelve months

Question. If the end A of a wire is irradiated with α -rays and the other end β is irradiated with b -rays. Then
(a) a current will flow from A to B
(b) a current will flow from B to A
(c) there will be no current in the wire
(d) a current will flow from each end to the mid-point of the wire

Question. Which of the following is best nuclear fuel
(a) thorium 236
(b) plutonium 239
(c) uranium 236
(d) neptunium 239

Question. In the process of fission, the binding energy per nucleon
(a) increases
(b) decreases
(c) remains unchanged
(d) increases for mass number A < 56 nuclei but decreases for mass number A > 56 nuclei

Question. Fusion reaction occurs at temperatures of the order of
(a) 10³ K
(b) 10⁷ K
(c) 10 K
(d) 10⁴ K

Question. One curie is equal to
(a) 3.7 × 10¹⁰ disintegration/sec
(b) 3.2 × 10⁸ disintegration/sec
(c) 2.8 × 10¹⁰ disintegration/sec
(d) None of these

Question. Nucleus of an atom whose atomic mass is 24 consists of
(a) 11 electrons, 11 protons and 13 neutrons
(b) 11 electrons, 13 protons and 11 neutrons
(c) 11 protons and 13 neutrons
(d) 11 protons and 13 electrons

Question. Which of the following nuclear reactions is not possible?

Question. If Avogadro number is 6 × 10²³, then number of protons, neutrons and electrons in 14 gms of ₆C¹⁴ are respecitvely
(a) 36 × 10²³, 48 × 10²³, 36 × 10²³
(b) 36 × 10²³, 36 × 10²³, 36 × 10²³
(c) 48 × 10²³, 36 × 10²³, 48 × 10²³
(d) 48 × 10²³, 48 × 10²³, 36 × 10²³

Question. Fusion reaction takes place at high temperature because
(a) nuclei break up at high temperature
(b) atoms get ionised at high temperature
(c) kinetic energy is high enough to overcome the coulomb repulsion between nuclei
(d) molecules break up at high temperature

Question. A gamma ray photon creates an electron-positron pair. If the rest mass energy of an electron is 0.5 MeV and the total kinetic energy of the electron-positron pair is 0.78 MeV, then the energy of the gamma ray photon must be
(a) 0.78 MeV
(b) 1.78 MeV
(c) 1.28 MeV
(d) 0.28 MeV

Question. The half-life of radioactive Radon is 3.8 days. The time at the end of which (1/20)th of the Radon sample will remain undecayed is (given log₁₀e = 0.4343)
(a) 13.8 days
(b) 16.5 days
(c) 33 days
(d) 76 days

Question. Radioactive element decays to form a stable nuclide, then the rate of decay of reactant is

Question. A radioactive nuclide is produced at the constant rate of n per second (say, by bombarding a target with neutrons). The expected number N of nuclei in existence t seconds after the number is N₀ is given by

Where l is the decay constant of the sample

Question. A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are
(a) 3 β–particles
(b) 2 β–particles and 1 α–particle
(c) 3 β–particles and 1 α–particle
(d) 2 α–particles and 1 β–particle.

Question. If the distance between nuclei is 2 × 10^–13 cm, the density of nuclear material is
(a) 3.21 × 10^–12 kg/m³
(b) 1.6 × 10^–3 kg/m³
(c) 2 × 10⁹ kg/m³
(d) 1 × 10¹⁷ kg/m³

Question. From the following equations, pick out hte possible nuclear reactions.
(a) ₆C¹³ + ₁H¹ → ₆C¹⁴ + 4.3 MeV
(b) ₆C¹² + ₁H¹ → ₇N¹³ + 2 MeV
(c) ₇N¹⁴ + ₁H¹ → ₈O¹⁵ + 7.3 MeV
(d) ₉₂U²³⁵ + ₀n¹ → ₅₄X¹⁴⁰ + ₃₈Si⁹⁴ + ₂₀n¹ + γ + 200 MeV

Question. If 200 MeV energy is released in the fission of a single U²³⁵ nucleus, the number of fissions required per second to produce 1 kilowatt power shall be (Given 1eV = 1.6 × 10^–19 J)
(a) 3.125 × 10¹³
(b) 3.125 × 10¹⁴
(c) 3.125 × 10¹⁵
(d) 3.125 × 10¹⁶

Question. 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

Question. A heavy nucleus having mass number 200 gets disintegrated into two small fragments of mass number 80 and 120. If binding energy per nucleon for parent atom is 6.5 MeV and for daughter nuclei is 7 MeV and 8 MeV respectively, then the energy released in the decay is X × 110 MeV. Find the value of X.
(a) 3
(b) 4
(c) 2
(d) 1

Question. M_p denotes the mass of a proton and M_n that of a neutron. A given nucleus, of binding energy B, contains Z protons and N neutrons. The mass M(N, Z) of the nucleus is given by (c is the velocity of light)
(a) M(N, Z) = NM_n + ZM_p + B/c²
(b) M(N, Z) = NM_n + ZM_p – Bc²
(c) M(N, Z) = NM_n + ZM_p + Bc²
(d) M(N, Z) = NM_n + ZM_p – B/c²

Question. The half life of a radioactive isotope ‘X’ is 50 years. It decays to another element ‘Y’ which is stable. The two elements ‘X’ and ‘Y’ were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be
(a) 150 years
(b) 200 years
(c) 250 years
(d) 100 years

Question. If the nuclear radius of 27Al is 3.6 fermi, the approximate nuclear radius of 64Cu in fermi is
(a) 2.4
(b) 1.2
(c) 4.8
(d) 3.6

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

Question. The decay constant of radium is 4.28 × 10^–4 per year. Its half life will be
(a) 2000 years
(b) 1240 years
(c) 63 years
(d) 1620 years

Fill in the Blanks

Question. The process responsible for energy production in the sun is _________________.

Question. A radioactive isotope of silver has half life of 20 minutes. The fraction of the original activity that remain after one hour is _________________.

Question. In both the processes of nuclear fission an nuclear fusion, a certain mass disappears. This is called _________________.

Question. One atomic mass unit is defined as _________________ of mass of an atom of ₆C¹².

Question. The rest mass of a nucleus is _________________ than the sum of the rest masses of its constituent nucleons.

Question. Isotopes of an element are the atoms of an element which have _________________ but different atomic weights.

Question. Isotones are the nuclides which contains _________________.

Question. The Apsara reactor at the Bhabha Atomic Research Centre (BARC), Mumbai, uses _________________ as moderator.

Question. Isobars are the atoms of different element which have same _________________ but different atomic number.

We hope the above multiple choice questions for Class 12 Physics for Chapter 13 Nuclei provided above with answers based on the latest syllabus and examination guidelines issued by CBSE, NCERT and KVS are really useful for you. Nuclei is an important chapter in Class 12 as it provides very strong understanding about this topic. Students should go through the answers provided for the MCQs after they have themselves solved the questions. All MCQs have been provided with four options for the students to solve. These questions are really useful for the benefits of class 12 students. Please go through these and let us know if you have any feedback in the comments section.