# CBSE Class 12 Physics Nuclei MCQs

## Nuclei Class 12 Physics MCQ

Class 12 Physics students should refer to the following multiple-choice questions with answers for Nuclei in standard 12. These MCQ questions with answers for Grade 12 Physics will come in exams and help you to score good marks

### Nuclei MCQ Questions Class 12 Physics with Answers

Question : The constituents of nucleus are

(a) electrons and protons
(b) protons and neutrons
(c) neutrons and electrons
(d) electrons, protons and neutrons

Question : The radius of a nucleus is

(a) directly proportional to its mass number
(b) inversely proportional to its atomic weight
(c) directly proportional to the cube root of its mass number
(d) None of these

Question : A nuclei having same number of neutron but different number of protons / atomic number are called

(a) isobars
(b) isomers
(c) isotones
(d) isotopes

Question : When the number of nucleons in nuclei increases, the binding energy per nucleon

(a) increases continuously with mass number
(b) decreases continuously with mass number
(c) remains constant with mass number
(d) first increases and then decreases with increase of mass number

Question : The mass of an atomic nucleus is less than the sum of the masses of its constituents. This mass defect is converted into

(a) heat energy
(b) light energy
(c) electrical energy
(d) energy which binds nucleons together

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

Question : On an average, the number of neutrons and the energy of a neutron released per fission of a uranium atom are respectively

(a) 2.5 and 2 keV
(b) 3 and l keV
(c) 2.5 and 2 MeV
(d) 2 and 2 keV

Question : A moderator is used in nuclear reactors in order to

(a) slow down the speed of the nuetrons
(b) acceleerate the neutrons
(c) increase the number of neutrons
(d) decrease the number of neutrons

Question : Fusion reactions take place at high temperature because

(a) atoms are ionised at high temperature
(b) molecules break up at high temperature
(c) nuclei break up at high temperature
(d) kinetic enrgy is high enough to overcome repulsion between nuclei

Question : For a nuclear fusion process, suitable nuclei are

(a) any nuclei
(b) heavy nuclei
(c) lighter nuclei
(d) nuclei lying in the middle of periodic table

Question : Chadwick was awarded the 1935 nobel prize in physics for his discovery of the
(a) electron
(b) proton
(c) neutron
(d) positron

Question : The element gold has
(a) 16 isotopes
(b) 32 isotopes
(c) 96 isotopes
(d) 173 isotopes

Question : The nuclear radius is of the order of
(a) 10–10 m
(b) 10–6 m
(c) 10–15 m
(d) 10–14 m

Question : Particles which can be added to the nucleus of an atom without changing its chemical properties are called
(a) neutrons
(b) electrons
(c) protons
(d) alpha particles

Question : The radius of a nucleus is
(a) directly proportional to its mass number
(b) inversely proportional to its atomic weight
(c) directly proportional to the cube root of its mass number
(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 : 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

Question : In ...X... water is circulated though the reactor vessel and transfers energy to steam generator in the ...Y... Here, X and Y refer to
(a) primary loop, secondary loop
(b) reactor core, turbine
(c) secondary loop, primary loop
(d) turbine, reactor core

Question : A nuclei having same number of neutron but different number of protons / atomic number are called
(a) isobars
(b) isomers
(c) isotones
(d) isotopes

Question : Which one of the following has the identical property for isotopes?
(a) Physical property
(b) Chemical property
(c) Nuclear property
(d) Thermal property

Question : The number of protons in an atom of atomic number Z and mass number A is
(a) zero
(b) Z
(c) A – Z
(d) A

Question : When the number of nucleons in nuclei increases, the binding energy per nucleon
(a) increases continuously with mass number
(b) decreases continuously with mass number
(c) remains constant with mass number
(d) first increases and then decreases with increase of mass number

Question : Mp denotes the mass of a proton and Mn 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) = NMn + ZMp + B/c2
(b) M(N, Z) = NMn + ZMp – Bc2
(c) M(N, Z) = NMn + ZMp + Bc2
(d) M(N, Z) = NMn + ZMp – B/c2

Question : Mass energy equation was propounded by
(a) Newton
(c) C. V. Raman
(d) Einstein

Question : The mass of an atomic nucleus is less than the sum of the masses of its constituents. This mass defect is converted into
(a) heat energy
(b) light energy
(c) electrical energy
(d) energy which binds nucleons together

Question : Which of the following statement is not true regarding Einsteins mass energy relation?
(a) Mass disappears to reappear as energy.
(b) Energy disappears to reappear as mass.
(c) Mass and energy are two different forms of the same entity.
(d) Mass and energy can never be related to each other.

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

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

Question : Nuclear forces exists between
(a) neutron - neutron
(b) proton - proton
(c) neutron - proton
(d) all of these

Question : The antiparticle of electron is
(a) positron
(b) α-particle
(c) proton
(d) β-particle

Question : Neutron decay in free space is given as follows 0n1 → 1H1 + -1e0 +[] Then the parenthesis [ ] represents a
(a) neutrino
(b) photon
(c) antineutrino
(d) graviton

(a) irreversible process
(b) self disintegration process
(c) spontaneous
(d) all of the above

Question : γ-rays are deflected by
(a) an electric field but not by a magnetic field
(b) a magnetic field but not by an electric field
(c) both electric and magnetic field
(d) neither by electric field nor by magnetic field

Question : Beta rays emitted by a radioactive material are
(b) the electrons orbiting around the nucleus
(c) charged particles emitted by nucleus
(d) neutral particles

Question : Which of the following is not a mode of radioactive decay ?
(a) Positron emission
(b) Electron capture
(c) Fusion
(d) Alpha decay

Question : The half-life period and the mean life period of a radioactive element are denoted respectively by Th and Tm. Then
(a) Th = Tm
(b) Th > T m
(c) Th < Tm
(d) Th ≥ Tm

Question : In γ 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 : Artificial radioactivity was discovered by
(a) Klaproth
(b) Rontgen
(c) Irene Curie and Joliot
(d) P. Curie and M. Curie

Question : Radioactive samples are stored in lead boxes because it is
(a) heavy
(b) strong
(c) good absorber

(a) physical changes
(b) chemical changes
(c) electric or magnetic fields
(d) all of the above

Question : A radioactive material undergoes decay by ejecting electrons. The electron ejected in this process is
(a) the electron from the decay of a neutron
(b) the electron present in the nucleus
(c) the resulting from the conversion of γ photon
(d) an orbital electron

Question : The same radioactive nucleus may emit
(a) all the three α, β and γ one after another
(b) all the three α, β and γ radiations simultaneously
(c) only α and β simultaneously
(d) only one α, β and γ at a time

Question : Which of the following of a radioactive material is a measure of its instability?
(a) Full life
(b) Mean life
(c) Half life
(d) None of these

Question : The rate of disintegration at a given instant, is directly proportional to the number of atoms present at that instant. This is the statement of
(b) half life
(d) group displacement law

Question : Fusion reactions take place at high temperature because
(a) atoms are ionised at high temperature
(b) molecules break up at high temperature
(c) nuclei break up at high temperature
(d) kinetic enrgy is high enough to overcome repulsion between nuclei

Question : Three specimens A, B, C of same radioactive element has activities 1 microcurie, 1 rutherford and 1 becquerel respectively. Which specimen has maximum mass?
(a) A
(b) B
(c) C
(d) all have equal masses

Question : Charge on an α-particle is
(a) 1.6 × 10–19 C
(b) 3.2 × 10–19 C
(c) 1.6 × 10–20 C
(d) 4.8 × 10–19 C

Question : If a radioactive element is placed in an evacuated chamber, then the rate of radioactive decay will
(a) decrease
(b) remains unchanged
(c) increase
(d) none of these

Question : The γ radiations are
(a) electromagnetic radiation with high energy
(b) electromagnetic radiation with low energy
(c) charged particles emitted by the nucleus
(d) electrons orbiting the nucleus

(a) α-rays
(b) β-rays
(c) γ-rays
(d) All of the above

Question : The 'rad' is the correct unit used to report the measurement of
(a) the ability of a beam of gamma ray photons to produce ions in a target
(b) the energy delivered by radiation to a target
(c) the biological effect of radiation
(d) the rate of decay of a radioactive source

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

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

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

Question : Control rods used in nuclear reactors are made of
(a) stainless steel
(b) graphite
(d) plutonium

Question : Boron rods in a nuclear reactor are used to
(a) absorb excess neutrons
(b) absorb alpha particle
(c) slow down the reaction
(d) speed up the reaction

Question : A moderator is used in nuclear reactors in order to
(a) slow down the speed of the nuetrons
(b) acceleerate the neutrons
(c) increase the number of neutrons
(d) decrease the number of neutrons

Question : If a star can convert all the He nuclei completely into oxygen nuclei. The energy released per oxygen nuclei is [Mass of He nucleus is 4.0026 amu and mass of Oxygen nucleus is 15.9994 amu]
(a) 7.6 MeV
(b) 56.12 MeV
(c) 10.24 MeV
(d) 23.9 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 : 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

(a) irreversible process
(b) self disintegration process
(c) spontaneous
(d) all of the above

Question : Beta rays emitted by a radioactive material are
(b) the electrons orbiting around the nucleus
(c) charged particles emitted by nucleus
(d) neutral particles

Question :  Which of the following is not a mode of a radioactive decay ?
(a) Positron emission
(b) Electron capture
(c) Fusion
(d) Alpha decay

Question : A radioactive material undergoes decay by ejecting electrons. The electron ejected in this process is
(a) the electron from the decay of a neutron
(b) the electron present in the nucleus
(c) the resulting from the conversion of g photon
(d) an orbital electron

Question : The rate of disintegration at a given instant, is directly proportional to the number of atoms present at that instant. This is the statement of
(b) half life
(d) group displacement law

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

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

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