# MCQs For NCERT Class 12 Physics Chapter 13 Nuclei

Please refer to the MCQ Questions for Class 12 Physics Chapter 13 Nuclei with Answers. The following Nuclei Class 12 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 12. Our experts have designed MCQ Questions for Class 12 Physics with Answers for all chapters in your NCERT Class 12 Physics book.

## Nuclei Class 12 MCQ Questions with Answers

See below Nuclei Class 12 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. If u denotes 1 atomic mass unit. One atom of an element has mass exactly equal to Au, where A is mass number of element.
(a) A = 1
(b) A = 12
(c) A = 16
(d) A can take up any integral value from 1 to 110

B

Question. A radioactive nucleus undergoes α -emission to form a stable element. What will be the recoil velocity of the daughter nucleus if v is the velocity of α emission?

A

Question. Which one is correct about fission?
(a) Approx. 0.1% mass converts into energy
(b) Most of energy of fission is in the form of heat
(c) In a fission of U235 about 200 eV energy is released
(d) On an average, one neutron is released per fission of U235

A

Question. If an electron and positron annihilate, then the energy released is
(a) 3.2´10-13 J
(b) 1.6´10-13 J
(c) 4.8´10-13 J
(d) 6.4´10-13 J

B

Question. The average binding energy per nucleon is maximum for the nucleus
(a) 2He4
(b) 8O16
(c) 26Fe56
(d) 92U238

C

Question. Half lives for α and β emission of a radioactive material are 16 years and 48 years respectively. When material decays giving α and β emission simultaneously, time in which 3/ 4th material decays is
(a) 29 years
(b) 24 years
(c) 64 years
(d) 12 years

B

Question. Radium 226Ra, spontaneously decays to radon with the emission of an a-particle and a g ray. If the speed of the a particle upon emission from an initially stationary radium nucleus is 1.5 ×107 m/s, what is the recoil speed of the resultant radon nucleus? Assume the momentum of g ray is negligible compared to that of a particle.
(a) 2..0 × 105 m/s
(b) 2.7 × 105 m/s
(c) 3.5 × 105 m/s
(d) 1.5 × 107 m/s

B

Question. A radioactive substance contains 10000 nuclei and its halflife period is 20 days. The number of nuclei present at the end of 10 days is
(a) 7070
(b) 9000
(c) 8000
(d) 7500

A

Question. The mass defect in a particular nuclear reaction is 0.3 grams. The amount of energy liberated in kilowatt hour is (Velocity of light = 3 × 108 m/s)
(a) 1.5 × 106
(b) 2.5 × 106
(c) 3 × 106
(d) 7.5 × 106

D

Question.In an a-decay the kinetic energy of a-particle is 48 MeV and Q-value of the reaction is 50 MeV. The mass number of the mother nucleus is X. Find value of X/25. (Assume that daughter nucleus is in ground state)
(a) 2
(b) 4
(c) 6
(d) 8

B

Question. The binding energies per nucleon for a deuteron and an a-particle are x1 and x2 respectively. What will be the energy Q released in the reaction 1H2 + 1H22He4 + Q
(a) 4(x1 + x2)
(b) 4(x2 – x1)
(c) 2(x1 + x2)
(d) 2(x2 – x1)

B

Question. The rest energy of an electron is
(a) 510 KeV
(b) 931 KeV
(c) 510 MeV
(d) 931 MeV

A

Question. Outside a nucleus
(a) neutron is stable
(b) proton and neutron both are stable
(c) neutron is unstable
(d) neither neutron nor proton is stable

D

Question. The electrons cannot exist inside the nucleus because
(a) de-Broglie wavelength associated with electron in β -decay is much less than the size of nucleus
(b) de-Broglie wavelength associated with electron in β -decay is much greater than the size of nucleus
(c) de-Broglie wavelength associated with electron in β -decay is equal to the size of nucleus
(d) negative charge cannot exist in the nucleus

B

Question. An element A decays into an element C by a two step process A → B+ 2He4 and B→ C + 2e . Then,
(a) A and C are isotopes
(b) A and C are isobars
(c) B and C are isotopes
(d) A and B are isobars

A

Question. For a nuclear fusion process, suitable nuclei are
(a) any Nuclei
(b) heavy Nuclei
(c) light Nuclei
(d) nuclei lying in the middle of periodic table

C

Question. Atomic number of a nucleus is Z and atomic mass is M. The number of neutron is
(a) M – Z
(b) M
(c) Z
(d) M + Z

A

Question. The mass and energy equivalent to 1 amu are respectively
(a) 1.67 × 10–27 gm, 9.30 MeV
(b) 1.67 × 10–27 kg, 930 MeV
(c) 1.67 × 10–27 kg, 1 MeV
(d) 1.67 × 10–34 kg, 1 MeV

B

Question. The volume of a nucleus is directly proportional to
(a) A
(b) A3
(c) √A
(d) A1/3

A

Question. The intensity of gamma radiation from a given source is I0. On passing through 37.5 mm of lead it is reduced to I0/8. The thickness of lead which will reduce it to I0/2 is
(a) (37.5)1/3 mm
(b) (37.5)1/4 mm
(c) 37.5/3 mm
(d) (37.5/4) mm

C

Question. The mass defect per nucleon is called
(a) binding energy
(b) packing fraction
(c) ionisation energy
(d) excitation energy

B

Question. Which of the following has the mass closest in value to that of the positron? (1 a.m.u. = 931 MeV)
(a) Proton
(b) Electron
(c) Photon
(d) Neutrino

B

Question. Radioactive substance emits
(a) α-rays
(b) β-rays
(c) ϒ-rays
(d) All of the above

D

Question. Nuclear forces are
(a) spin dependent and have no non-central part
(b) spin dependent and have a non-central part
(c) spin independent and have no non-central part
(d) spin independent and have a non-central part

B

Question. The curve of binding energy per nucleon as a function of atomic mass number has a sharp peak for helium nucleus. This implies that helium
(a) can easily be broken up
(b) is very stable
(c) can be used as fissionable meterial

B

Question. Half life of radioactive element depends upon
(a) amount of element present
(b) temperature
(c) pressure
(d) nature of element

D

Question. In the uranium radioactive series, the initial nucleus is 92U238 and that the final nucleus is 82Pb206. When uranium nucleus decays to lead, the number of α particles and β particles emitted are
(a) 8α, 6 β
(b) 6α, 7β
(c) 6α, 8β
(d) 4α, 3β

A

Question. An electron is
(b) baryon
(c) a nucleon
(d) a lepton.

D

Question. Actinium 231, 231 AC89, emit in succession two β particles, four α-particles, one β and one a 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. A freshly prepared radioactive source of half life 2 hr emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is
(a) 6 hr
(b) 12 hr
(c) 24 hr
(d) 128 hr

B

Question. If 1 mg of U235 is completely annihilated, the energy liberated is
(a) 9 × 1010 J
(b) 9 × 1019 J
(c) 9 × 1018 J
(d) 9 × 1017 J

A

Question. Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time t = 0, number of P species are 4 N0 and that of Q are N0. Half-life of P (for conversion to R) is 1 minute where as that of Q is 2 minutes. Initially there are no nuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be

B

Question. A mixture consists of two radioactive materials A1 and A2 with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of A1 and 160 g of A2. The amount of the two in the mixture will become equal after
(a) 60 s
(b) 80 s
(c) 20 s
(d) 40 s

D

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

B

Question. Fraction of tritium left after 150 years (half life of tritium is 12.5 years) is
(a) 1/ 1024
(b) 1/2048
(c) 1/4096
(d) 1/8192

C

Question. The half life of the radioactive substance is 40 days. The substance will disintegrate completely in
(a) 40 days
(b) 400 days
(c) 4000 days
(d) infinite time

Question. A radioactive sample with a half life of 1 month has the label : ‘Activity = 2 micro curies on 1–8–1991. What would be its activity two months earlier ?
(a) 1.0 micro curie
(b) 0.5 micro curie
(c) 4 micro curie
(d) 8 micro curie

D

Question. Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material with a half life of 1 yr. After 1 year,
(a) all the containers will have 5000 atoms of the material
(b) all the contains will conatin 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

C

Question. A duetron strikes 8O16 nucleus with subsequent emission of alpha particle. Identify the nucleus so produced
(a) 3Li7
(b) 5B10
(c) 7N13
(d) 7N14

D

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 γ- radioactivity
(c) change for α-radioactivity but not for others
(d) change for β-radioactivity but not for others

B

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 force between neutrons are weaker than that between protons

B

Question. A radio isotope ‘X’ with a half life 1.4 × 109 years decays to ‘Y’ which is stable. A sample of the rock from a cave was found to contain ‘X’ and ‘Y’ in the ratio 1 : 7. The age of the rock is :
(a) 1.96 × 109 years
(b) 3.92 × 109 years
(c) 4.20 × 109 years
(d) 8.40 × 109 years

C

Question. A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 a.m.u. The energy liberated per a.m.u. is (Given : 1 a.m.u = 931 MeV)
(a) 26.7 MeV
(b) 6.675 MeV
(c) 13.35 MeV
(d) 2.67 MeV

B

Question. A certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 a.m.u. The energy liberated per a.m.u. is (Given : 1 a.m.u = 931 MeV)
(a) 26.7 MeV
(b) 6.675 MeV
(c) 13.35 MeV
(d) 2.67 MeV

B

Question. The more readily fissionable isotope of uranium has an atomic mass of
(a) 234
(b) 235
(c) 236
(d) 238

B

Question. A radioactive nucleus of mass M emits a photon of frequency n and the nucleus recoils. The recoil energy will be
(a) Mc2 – hn
(b) h2n2 / 2Mc2
(c) zero
(d) hn

B

Question. The half life of a radioactive isotope ‘X’ is 20 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 : 7 in a sample of a the given rock. The age of the rock is estimated to be
(a) 60 years
(b) 80 years
(c) 100 years
(d) 40 years

A

Question. How does the binding energy per nucleon vary with the increase in the number of nucleons?
(a) Increases continuously with mass number
(b) Decreases continuously with mass number
(c) First decreases and then increases with increase in mass number
(d) First increases and then decreases with increase in mass number

D

Question. A nucleus of uranium decays at rest into nuclei of thorium and helium. Then :
(a) the helium nucleus has less momentum than the thorium nucleus.
(b) the helium nucleus has more momentum than the thorium nucleus.
(c) the helium nucleus has less kinetic energy than the thorium nucleus.
(d) the helium nucleus has more kinetic energy than the thorium nucleus

D

Question. The half life of a radioactive isotope ‘X’ is 20 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 : 7 in a sample of a the given rock. The age of the rock is estimated to be
(a) 60 years
(b) 80 years
(c) 100 years
(d) 40 years

A

Question. Tritium is an isotope of hydrogen whose nucleus Triton contains 2 neutrons and 1 proton. Free neutrons decay into p + ē + v–. If one of the neutrons in Tritium decays, it would transform into 2He3 nucleus. This does not happen. This is because
(A) tritium 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.

A

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

B

Question. ___________ has the mass closest to the mass of positron.
(A) Proton
(B) Neutron
(C) Electron
(D) Neutrino

C

Question. Heavy stable nucleus 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.

B

Question. Nuclear force is a ___________ and ___________ force.
(A) Strong, long-range
(B) Strong, short range
(C) Weak, long-range
(D) Weak, short-range

B

Question. X amount of energy is required to remove an electron from its orbit and Y amount of energy is required to remove a nucleon from the nucleus.
(A) X = Y
(B) X > Y
(C) Y > X
(D) X ≥ Y

C

Question. The mass of a nucleus in its ground state is
(A) less than the total mass of neutrons and protons.
(B) greater than the total mass of neutrons and protons.
(C) equal to the total mass of neutrons and protons.
(D) equal to the total mass of neutron, protons and electrons.

A

Question. Which of the following material will be the best moderator for a nuclear power plant?
(A) Lighter element
(B) Heavier element
(C) Both of the above
(D) None of the above

A

Question. Two nuclei have mass number in the ratio 1 : 2. The ratio of their nuclear densities is
(A) 1 : 2
(B) 2 : 1
(C) 1 : 1
(D) Cannot be defined from mass number ratio

C

Assertion and Reason Based MCQs

Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R).
Mark the correct choice as:
(A) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.

Question. Assertion (A): Electrons do not experience strong nuclear force.
Reason (R): Strong nuclear force is charge independent.

B

Question. Assertion (A): Two atoms of different elements having same mass number but different atomic numbers are called isobars.
Reason (R): Atomic number is the number of protons present and atomic number is the total number of protons and neutrons present in a nucleus.

B

Question. Assertion (A): The binding energy per nucleon, for nuclei with mass number (A) > 56 decreases with A.
Reason (R):
Nuclear force is weak in heavier nuclei.

C

Question. Assertion (A): Nuclear force is same between neutron-neutron, proton-proton and neutronproton.
Reason (R): Nuclear force is charge independent.

A

Question. Assertion (A): Density of all the nuclei is same.
Reason (R): Radius of nucleus is directly proportional to the cube root of mass number.

A

Case-based MCQs

I. Read the following text and answer the following questions on the basis of the same:
India’s atomic energy programme :
The atomic energy programme in India was launched around the time of independence under the leadership of Homi J. Bhabha (1909-1966). An early historic achievement was the design and construction of the first nuclear reactor in India (named Apsara) which went critical on August 4, 1956. India indigenously designed and constructed plutonium plant at Trombay, which ushered in the technology of fuel reprocessing (separating useful fissile and fertile nuclear materials from the spent fuel of a reactor). Research reactors that have been subsequently commissioned include ZERLINA, PURNIMA (I, II and III), DHRUVA and KAMINI. KAMINI is the country’s first large research reactor that uses U-233 as fuel. The main objectives of the Indian Atomic Energy programme are to provide safe and reliable electric power for the country’s social and economic progress and to be self reliant in all aspects of nuclear technology. Exploration of atomic minerals in India undertaken since the early fifties has indicated that India has limited reserves of uranium, but fairly abundant reserves of thorium. Accordingly, our country has adopted a three stage strategy of nuclear power generation. The first stage involves the use of natural uranium as a fuel, with heavy water as moderator. The Plutonium- 239 obtained from reprocessing of the discharged fuel from the reactors then serves as a fuel for the second stage — the fast breeder reactors. They are so called because they use fast neutrons for sustaining the chain reaction (hence no moderator is needed) and, besides generating power, also breed more fissile species (plutonium) than they consume. The third stage, most significant in the long term, involves using fast breeder reactors to produce fissile Uranium-233 from Thorium-232 and to build power reactors based on them.

Question. The main objectives of the Indian Atomic Energy programme :
(A) Development of Nuclear weapons for success in warfare
(B) Generation of safe and reliable electric power
(C) Efficient medical treatment
(D) To breed more fissile species

B

Question. India’s atomic energy programme was launched by:
(A) Shanti Swarup Bhatnagar
(B) Homi J. Bhabha
(D) Daulat Singh Kothari

B

Question. Which one of the following is not a nuclear reactor ?
(A) PURNIMA
(B) DHRUVA
(C) KAMINI
(D) ARYABHATTA

D

Question. India has limited reserves of ……………., but fairly abundant reserves of …………….. :
(A) Plutonium, Thorium
(B) Thorium, Uranium
(C) Plutonium, Uranium
(D) Uranium, Thorium

D

Question. First nuclear reactor of India :
(A) APSARA
(B) ZERLINA
(C) DHRUBA
(D) KAMINI

A

II. Read the following text and answer the following questions on the basis of the same:
Grand Unification Theory :
There are four fundamental forces in the universe :
Gravitational force
Electromagnetic force
The weak nuclear force
The strong nuclear force
The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles.
Gravitational force and Electromagnetic force have infinite range.
The Four fundamental forces and their strengths
(i) Gravitational Force – Weakest force; but has infinite range.
(ii) Weak Nuclear Force – Next weakest; but short range.(iii) Electromagnetic Force – Stronger, with infinite range.
(iv) Strong Nuclear Force – Strongest; but short range.
Unification :
The weak nuclear force and electromagnetic force have been unified under the Standard Electroweak Theory, (Glashow, Weinberg and Salaam were awarded the Nobel Prize for this in 1979).
Grand unification theories attempt to treat both strong nuclear force and electroweak force under the same mathematical structure.
Theories that add gravitational force to the mix and try to unify all four fundamental forces into a single force are called Superunified Theories. It has not yet been successful.

Question. Which one is the weakest force ?
(A) Weak nuclear force
(B) Electromagnetic force
(C) Strong magnetic force
(D) Gravitational force

D

Question. Which fundamental force is always attractive ?
(A) Electric force
(B) Magnetic force
(C) Gravitational force
(D) Strong nuclear force

C

Question. Which of the following forces have infinite ranges?
(A) Weak nuclear force and strong nuclear force
(B) Gravitational force and Electromagnetic force
(C) Weak nuclear force and Gravitational force
(D) All the forces

B

Question. What are the 4 fundamental forces ?
(A) Gravitational force, electromagnetic force, nuclear force, Tension force
(B) Gravitational force, electromagnetic force, nuclear force, Frictional force
(C) Gravitational force, electromagnetic force, weak nuclear force, strong nuclear force
(D) Frictional force, electric force, nuclear force, magnetic force