MCQ On Class 12 Physics Chapter 13 Nuclei

1 The Bohr model of atoms

A assumes that the angular momentum of elec-trons is quantized.

B uses Einstein’s photoelectric equation.

C predicts continuous emission spectra for at-oms.

D predicts the same emission spectra for all types of atoms.

Answer:assumes that the angular momentum of elec-trons is quantized.

2 According to Yukawa’s theory of nuclear forces, the origin of nuclear force between nucleons is due to the exchange of

A mesons

B photons

C electrons

D positrons

View Answer

Answer:photons

3 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

View Answer

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

4 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

View Answer

Answer:α, β, γ

5 The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an

A isomer of parent

B isotone of parent

C isotope of parent

D isobar of parent

View Answer

Answer:isotope of parent

6 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

View Answer

Answer:27

7 In nuclear reactors, the control rods are made of

A cadmium

B graphite

C krypton

D plutonium

View Answer

Answer:cadmium

8 The half life of a radioactive susbtance is 30 days. What is the time taken to disintegrate to 3/4^th of its original mass?

A 30 days

B 15 days

C 60 days

D 90 days

View Answer

Answer:60 days

9 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

View Answer

Answer:10¹¹ kg m^-3

10 An electron emitted in beta radiation originates from

A inner orbits of atom

B free electrons existing in the nuclei

C decay of a neutron in a nuclei

D photon escaping from the nucleus

View Answer

Answer:decay of a neutron in a nuclei

11 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

View Answer

Answer:2.29 × 10¹⁷ kg m^-3

12 The equation 4₁ ¹H⁺ → 2⁴He²⁺ + 2e^– + 26 MeV represents

A β-decay

B γ-decay

C fusion

D fission

View Answer

Answer:fusion

13 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

View Answer

Answer:A and C are isotopes

14 Complete the series 6He → e^– + ⁶Li +

A neutrino

B antineutrino

C proton

D neutron

View Answer

Answer:antineutrino

15 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

View Answer

Answer:joining of nuclei

16 In nuclear reaction, there is conservation of

A mass only

B energy only

C momentum only

D mass, energy and momentum

View Answer

Answer:mass, energy and momentum

17 Alpha particle emitted from a radioactive material are:

A Helium nuclei

B Hydrogen nuclei

C Lithium nuclei

D None of the above

View Answer

Answer:Helium nuclei

18 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

View Answer