Q. When a β-particle is emitted from a nucleus then its neutron-proton ratio
✅ Correct Answer: (B)
decreases
Nuclei MCQs with answers
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Q. The quantity which is not conserved in a nuclear reaction is
✅ Correct Answer: (C)
mass
Q. A radioactive nucleus emits a beta particle. The parent and daughter nuclei are
✅ Correct Answer: (D)
isobars
Q. In the disintegration series
the values of Z and A respectively will be
the values of Z and A respectively will be
✅ Correct Answer: (D)
91, 234
Q. A nucleus AZX emits an α-particle. The resultant nucleus emits a β-particle. The respective atomic and mass numbers of the daughter nucleus will be
✅ Correct Answer: (B)
Z – 1, A – 4
Q. The mass number of iron nucleus is 56 the nuclear density is
✅ Correct Answer: (B)
2.29 × 1017 kg m-3
Q. 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?
✅ Correct Answer: (A)
27
Q. The half life of a radioactive substance is 30 days. What is the time taken to disintegrate to 3/4th of its original mass?
✅ Correct Answer: (C)
60 days
Q. 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
✅ Correct Answer: (C)
isotope of parent
Q. During negative β-decay, an antineutrino is also emitted along with the emitted electron. Then,
✅ Correct Answer: (D)
total linear momentum, total angular momentum and total energy will be conserved
Q. 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
✅ Correct Answer: (A)
α, β, γ
Q. An electron emitted in beta radiation originates from
✅ Correct Answer: (C)
decay of a neutron in a nuclei
Q. An element A decays into an element C by a two step process A → B+ 2He4 and B → C + 2e–. Then,
✅ Correct Answer: (A)
A and C are isotopes
Q. P-rays emitted by a radioactive material are
✅ Correct Answer: (D)
charged particles emitted by nucleus
Q. In a β-decay
✅ Correct Answer: (C)
the daughter nucleus has one proton more than the parent nucleus.
Q. When a radioactive nucleus emits a (β-particle, the mass number of the atom:
✅ Correct Answer: (B)
remains the same.
Q. In an α-decay
✅ Correct Answer: (C)
the daughter nucleus has two protons less than parent nucleus.
Q. Which of the following are not emitted by radioactive substances?
✅ Correct Answer: (B)
Protons
Q. 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?
✅ Correct Answer: (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.
Q. Heavy stable nuclei have more neutrons than protons. This is because of the fact that
✅ Correct Answer: (B)
electrostatic force between protons are repulsive.
Q. In nuclear reaction, there is conservation of
✅ Correct Answer: (D)
mass, energy and momentum
Q. 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,
✅ Correct Answer: (C)
the containers will in general have different numbers of the atoms of the material but their average will be close to 5000.
Q. When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom
✅ Correct Answer: (B)
change for α and β radioactivity but not for γ-radioactivity.
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