## Class 12 Physics MCQs Nuclei for JEE/NEET

Here, you will get Class 12 Physics MCQ of Chapter 13 Nuclei for cracking JEE and NEET/AIIMS. By solving these MCQs of Class 12 Physics Chapter 13 Nuclei, you will get the confidence to crack JEE or NEET. Practice MCQ Questions for Class 12 Physics with Answers on a daily basis and score well in exams.

## Nuclei Class 12 MCQs Questions with Answers

A radioactive nucleus emits a beta particle. The parent and daughter nuclei are
(a) isotopes
(b) isotones
(c) isomers
(d) isobars

Order of magnitude of density of uranium nucleus is
(a) 1020 kg m-3
(b) 1017 kg m-3
(c) 1014 kg m-3
(d) 1011 kg m-3

The mass number of iron nucleus is 56 the nuclear density is
(a) 2.29 × 1016 kg m-3
(b) 2.29 × 1017 kg m-3
(c) 2.29 × 1018 kg m-3
(d) 2.29 × 1015 kg m-3

Answer: (b) 2.29 × 1017 kg m-3

The radius of a spherical nucleus as measured by electron scattering is 3.6 fm. What is the mass number of the nucleus most likely to be?
(a) 27
(b) 40
(c) 56
(d) 120

During negative β-decay, an antineutrino is also emitted along with the emitted electron. Then,
(a) only linear momentum will be conserved
(b) total linear momentum and total angular momentum but not total energy will be conserved
(c) total linear momentum, and total energy but not total angular momentum will conserved
(d) total linear momentum, total angular momentum and total energy will be conserved

Answer: (d) total linear momentum, total angular momentum and total energy will be conserved

Consider α and β particles and γ-rays each having an energy of 0.5 MeV. In the increasing order of penetrating power, the radiation are respectively
(a) α, β, γ
(b) α, γ, β
(c) β, γ, α
(d) γ β, α

When the mass of a sample of a radioactive substance decreases, the mean life of the sample
(a) increases
(b) decreases
(c) remain unchanged
(d) first decreases then increases

Rutherford is the unit of
(b) energy
(c) photoelectric current
(d) magnetic field

An electron and a positron each having a mass equivalent to 0.53 MeV annihilate each other and produce a photon. The minimum energy of the photon is
(a) 0.53 MeV
(b) 1.06 MeV
(c) 2.12 MeV
(d) zero

Radius of 1st Bohr orbit is a0 (= 0.529 Å) What is the radius of 2nd Bohr orbit?
(a) 10-8
(b) 2a0
(c) 4a0
(d) 2√2a0

Alpha particle emitted from a radioactive material are
(a) Helium nuclei
(b) Hydrogen nuclei
(c) Lithium nuclei
(d) None of the above

The half life of a radioactive decay is n times its mean life, n is equal to
(a) 0.6930
(b) 0.0693
(c) 1/0.6930
(d) 0.3070

The Bohr model of atom
(a) assumes that the angular momentum of electron is quantized
(b) uses Einstein’s photoelectric equation
(c) predicts continuous emission spectra for atoms
(d) predicts the same emission spectra for all types of atoms

Answer: (a) assumes that the angular momentum of electron is quantized

Nuclear force is
(a) strong, short range and charge independent force
(b) charge independent, attractive and long range force
(c) strong, charge dependent and short range attractive force
(d) long range, change dependent and attractive force

Answer: (a) strong, short range and charge independent force

The binding energies of the atoms of elements A and B are Ea and Eb respectively. Three atoms of the elements B fuse to give one atom of element A. This fusion process is accompained by release of energy E. Then Ea, Eb and E are related to each other as
(a) Ea + E = 3 Eb
(b) Ea = 3Eb
(c) Ea – E = 3 Eb
(d) Ea + 3Eb + E = 0

Answer: (a) Ea + E = 3 Eb

One requires an energy En to remove a nucleon from a nucleus and an energy Ee to remove an electron from an atom. Then
(a) En = Ee
(b) En > Ee
(c) En < Ee
(d) En > Ee.

If 10 % of a radioactive material decays in 5 days, then the amount of the original material left after 20 days is nearly
(a) 60%
(c) 75%
(b) 70%
(d) 66%

Maximum permissible radiation dose a a person may have with no adverse effects is
(a) 250 × 10-1 roentgen’s per week
(b) 250 × 10-2 roentgen’s per week
(c) 250 × 10-3 roentgen’s per week
(d) 250 roentgen’s per week

Answer: (c) 250 × 10-3 roentgen’s per week

If the atomic masses for the parent and daughter element in a radioactive decay are Mp and Md and the mass of the electron me then the Q-value for the radioactive ß decay is given by
(a) Q = Mp C²
(b) Q = (Mp – Md – Mc) C²
(c) Q = (Mp – Md)C²
(d) Q = (Mp – md – 2Me)C²

Answer: (c) Q = (Mp – Md)C²

Which of the following is the best nuclear fuel
(a) Thorium-236
(b) Plutonium – 239
(c) Neptunium-239
(d) Uranium-236

Samples of two radioactive nuclides A and B are taken λA and λB 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 λA = λB
(b) Initial rate of decay of A is less than the initial rate of decay of B and λA < λB
(c) Initial rate of decay of B is twice the initial rate of decay of A and λA > λB
(d) Initial rate of decay of B is same as the rate of decay of A at t = 2h and λB = λA

Answer: (d) Initial rate of decay of B is same as the rate of decay of A at t = 2h and λB = λA

If radio active nuclei emits β-particle, then mass-number
(a) increased by 1 unit
(b) decreases by 1 unit
(c) increases by 2 unit
(d) decreases by 2 unit

Answer: (a) increased by 1 unit

Fusion takes place at high temperature because
(a) Atom are ionised at high temperature
(b) Molecules break up at high temperature
(c) Nuclei break up at high temp.
(d) Kinetic energy is high enough to overcome repulsion between nuclei

Answer: (d) Kinetic energy is high enough to overcome repulsion between nuclei

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

Answer: (c) the containers will in general have different numbers of the atoms of the material but their average will be close to 5000

Light energy emitted by star is due to
(a) breaking of nuclei
(b) joining of nuclei
(c) burning of nuclei
(d) reflection of solar light