Nuclei Objective Questions
- 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
Answer: (a) A and C are isotops
2. 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
Answer: (b) joining of nuclei
3. In nuclear reaction, there is conservation of
(a) mass only
(b) energy only
(c) momentum only
(d) mass, energy and momentum
Answer: (d) mass, energy and momentum
4. In nuclear reactors, the control rods are made of
(a) cadmium
(b) graphite
(c) krypton
(d) plutonium
Answer: (a) cadmium
5. The mass number of iron nucleus is 56 the nuclear density is
(a) 2.29 × 1016 kgm-3
(b) 2.29 × 1017 kgm-3
(c) 2.29 × 1018 kgm-3
(d) 2.29 × 1015 kgm-3
Answer: (b) 2.29 × 1017 kgm-3
6. 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
Answer: (b) 1017 kg m-3
7. 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
Answer: (a) 27
8. The half life of a radioactive susbtance is 30 days. What is the time taken to disintegrate to 3/4th of its original mass?
(a) 30 days
(b) 15 days
(c) 60 days
(d) 90 days
Answer: (c) 60 days
9. 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
Answer: (c) isotope of parent
10. 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
11. 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
Answer: (c) decay of a neutron in a nuclei
12. Complete the series 6He → e– + 6Li+
(a) neutrino
(b) antineutrino
(c) proton
(d) neutron
Answer: (b) antineutrino
13. 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
Answer: (a) α, β, γ
14. Atomic number decreases with the emission of a particles from the nucleus :
(A) 1
(B) 2
(C) 3
(D) 4
Answer: (B) 2
15. Density of nucleus is about :
(A) 2.29 x 107 kg m-3
(B) 2.29 x 10-7 kg m-3
(C) 2.29 x 1017 kg m-3
(D) 2.29 x 10-17 kg m-3
Answer: (C) 2.29 x 1017 kg m-3
16. Which of the relations is correct for radioactive atom ?
(A) Half-life = Average life
(B) Half-life = 2 x Average life
(C) Half-life = 1.6931 x Average life
(D) Half-life = 0.6931 x Average life
Answer: (D) Half-life = 0.6931 x Average life
17. The equivalent energy of 1 g of substance is :
(A) 9 x 1013 J
(B) 6 x 1012 J
(C) 3 x 1013 J
(D) 6 x 1013 J
Answer: (A) 9 x 1013 J
18. X-ray was discovered by:
(A) Becqueral
(B) Marie curie
(C) Roengton
(D) Vanlaw
Answer: (C) Roengton
19. The order of nuclear density is :
(A) 103
(B) 1017
(C) 106
(D) None
Answer: (B) 1017
20. If R is the radius and A is the mass of a nucleus then the graph of log R versus log A will be:
(A) A straight line
(B) A parabola
(C) An Ellipse’
(D) None of these
Answer: (B) A parabola
21. The time in which radioactive substance become half of its intial amount is called :
(A) average life
(B) half-life
(C) time-period
(D) decay constant
Answer: (B) half-life
22. Mass is converted into energy according to the relation :
(A) E = mc2
(B) E = mgh
(c) E = 1/2 mc2
(D) E = mgh / c2
Answer: (A) E = mc2
23. Who discovered heavy Hydrogen ?
(A) Uray
(B) Thomson
(C) Mosley
(D) Fermi
Answer: (A) Uray
24. Which of the following is not a mode of radioactive decay ?
(A) positron emission
(B) electron capture
(C) fusion
(D) alpha decay
Answer: (C) fusion
25. Which one of the following has maximum penetraing power:
(A) X-rays
(B) cathode rays
(C) α-rays
(D) Y-rays
Answer: (D) Y-rays
26. Time during which the amount of radioactive substance becomes half of its initial amount is called.
(A) Average life
(B) Half life
(c) Decay constant
(D) Time period
Answer: (B) Half life
