24 + Interview Questions in THE NUCLEUS IN GENERAL AWARENESS Page 1 InterviewSolution

1.	As the mass number A increases, which of the following quantities related to a nucleus do not change?(a) mass (b) volume (c) density (d) binding energy.
Answer» (c) Nucleus do not change density.

Discussion

2.	A freshly prepared radioactive source of half-life 2h 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) 6h (b) 12h (c) 24h (d) 128h.
Answer» (b) The minimum time after which it would be possible to work safely with this source is 12h.

Discussion

3.	During a negative beta decay, (a) an atomic electron is ejected (b) an electron which is already present within the nucleus is ejected (c) a neutron in the nucleus decays emitting an electron(d) a proton in the nucleus decays emitting an electron.
Answer» (c) a neutron in the nucleus decays emitting an electron

Discussion

4.	The decay constant of a radioactive sample is X. The half-life and the average-life of the sample are respectively(a) 1/λ and (In 2/λ) (b) (In 2/λ) and 1/λ(c) λ(ln 2) and 1/λ (d) λ/(ln 2) and 1/λ.
Answer» The correct answer is (b) (In 2/λ) and 1/λ

Discussion

5.	In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following particles is emitted in the decay? (a) proton (b) neutron (c) electron (d) photon.
Answer» The correct answer is (d) photon.

Discussion

6.	The masses of 11C and 11B are respectively 11.0114 u and 11.0093 u. Find the maximum energy a positron can have in the β+-decay of 11C to 11B.
Answer» ''C →''B +β⁺+ v mass of C'' = 11.014u ; mass of B'' = 11.0093u Energy liberated = (11.014 – 11.0093)u = 29.5127 Mev. For maximum K.E. of the positron energy of v may be assumed as 0. Maximum K.E. of the positron is 29.5127 Mev.

6.

The masses of 11C and 11B are respectively 11.0114 u and 11.0093 u. Find the maximum energy a positron can have in the β+-decay of 11C to 11B.

Answer»

''C →''B +β⁺+ v

mass of C'' = 11.014u ; mass of B'' = 11.0093u

Energy liberated = (11.014 – 11.0093)u = 29.5127 Mev.

For maximum K.E. of the positron energy of v may be assumed as 0.

Maximum K.E. of the positron is 29.5127 Mev.

Discussion

7.	How much energy is released in the following reaction?7Li+p→α+αAtomic mass of 7Li - 7.0160 u and that of 4He - 4.0026 u.
Answer» Li⁷ + p → l + α + E ; Li⁷ = 7.016u α= ⁴He = 4.0026u ; p = 1.007276 u E = Li⁷ + P – 2α = (7.016 + 1.007276)u – (2x 4.0026)u = 0.018076 u. =>0.018076 x 931 = 16.828 = 16.83 MeV.

7.

How much energy is released in the following reaction?7Li+p→α+αAtomic mass of 7Li - 7.0160 u and that of 4He - 4.0026 u.

Answer»

Li⁷ + p → l + α + E ; Li⁷ = 7.016u

α= ⁴He = 4.0026u ; p = 1.007276 u

E = Li⁷ + P – 2α = (7.016 + 1.007276)u – (2x 4.0026)u = 0.018076 u.

=>0.018076 x 931 = 16.828 = 16.83 MeV.

Discussion

8.	As the mass number A increases, the binding energy per nucleon in a nucleus(a) increases (b) decreases (c) remains the same (d) varies in a way that depends on the actual value of A.
Answer» (d) varies in a way that depends on the actual value of A.

Discussion

9.	Find the binding energy per nucleon of (197,79)Au if its atomic mass is 196.96 u.
Answer» B = (Zmp + Nmn – M)C² Z = 79 ; N = 118 ; m_p = 1.007276u ; M = 196.96 u ; m_n = 1.008665u B = [(79 x 1.007276 + 118 x 1.008665)u – Mu]c² = 198.597274 x 931 – 196.96 x 931 = 1524.302094 so, Binding Energy per nucleon = 1524.3 / 197 = 7.737.

9.

Find the binding energy per nucleon of (197,79)Au if its atomic mass is 196.96 u.

Answer»

B = (Zmp + Nmn – M)C²

Z = 79 ; N = 118 ; m_p = 1.007276u ; M = 196.96 u ; m_n = 1.008665u

B = [(79 x 1.007276 + 118 x 1.008665)u – Mu]c²

= 198.597274 x 931 – 196.96 x 931 = 1524.302094

so, Binding Energy per nucleon = 1524.3 / 197 = 7.737.

Discussion

10.	Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because(a) a lithium nucleus is more tightly bound than a carbon nucleus(b) carbon nucleus is an unstable particle(c) it is not energetically favourable(d) Coulomb repulsion does not allow the nuclei to come very close.
Answer» (d) Coulomb repulsion does not allow the nuclei to come very close.

Discussion

11.	Consider a sample of a pure beta-active material. (a) All the beta particles emitted have the same energy. (b) The beta particles originally exist inside the nucleus and are ejected at the time of beta decay. (c) The antineutrino emitted in a beta decay has zero mass and hence zero momentum. (d) The active nucleus changes to one of its isobars after the beta decay.
Answer» (d) The active nucleus changes to one of its isobars after the beta decay.

Discussion

12.	In which of the following decays the element does not change?(a) α-decay (b) β -decay (c) β -decay (d) γ-decay.
Answer» (d) The element does not change γ-decay.

Discussion

13.	Which of the following are electromagnetic waves? (a) α -rays (b) beta-plus rays(c) beta-minus rays (d) gamma rays.
Answer» (d) gamma rays.

Discussion

14.	Magnetic field does not cause deflection in (a) α-rays (b) beta-plus rays (c) beta-minus rays (d) gamma rays.
Answer» (d) gamma rays.

Discussion

15.	During a nuclear fission reaction, (a) a heavy nucleus breaks into two fragments by itself (b) a light nucleus bombarded by thermal neutrons breaks up (c) a heavy nucleus bombarded by thermal neutrons breaks up (d) two light nuclei combine to give a heavier nucleus and possibly other products.
Answer» (c) a heavy nucleus bombarded by thermal neutrons breaks up

Discussion

16.	The graph of In(R/R0) versus In A (R = radius of a nucleus and A = its mass number) is(a) a straight line (b) a parabola(c) an ellipse (d) none of them.
Answer» (a) a straight line

Discussion

17.	The mass number of a nucleus is(a) always less than its atomic number(b) always more than its atomic number(c) equal to its atomic number(d) sometimes more than and sometimes equal to its atomic number.
Answer» (d) sometimes more than and sometimes equal to its atomic number.

Discussion

18.	Two protons are kept at a separation of 10nm. Let Fn and Fe be the nuclear force and the electromagnetic force between them.(a )Fe = Fn (b)Fe >> Fn (c )Fe << Fn(d) Fe and Fn differ only slightly.
Answer» The correct answer is(b)Fe >> Fn

Discussion

19.	As compared to 12C atom, 14C atom has(a) two extra protons and two extra electrons(b) two extra protons but no extra electron(c) two extra neutrons and no extra electron(d) two extra neutrons and two extra electrons.
Answer» (c) two extra neutrons and no extra electron

Discussion

20.	The mass number of a nucleus is equal to(a) the number of neutrons in the nucleus(b) the number of protons in the nucleus(c) the number of nucleons in the nucleus(d) none of them.
Answer» (c) the number of nucleons in the nucleus

Discussion

21.	The mass of a neutral carbon atom in ground state is (a) exact 12u (b) less than 12u(c) more than 12u(d) depends on the form of carbon such as graphite or charcoal.
Answer» (a) exact 12u

Discussion

22.	In one average-life,(a) half the active nuclei decay(b) less than half the active nuclei decay(c) more than half the active nuclei decay(d) all the nuclei decay.
Answer» (c) more than half the active nuclei decay

Discussion

23.	Which of the following is a wrong description of binding energy of a nucleus? (a) It is the energy required to break a nucleus into its constituent nucleons. (b) It is the energy made available when free nucleons combine to form a nucleus. (c) It is the sum of the rest mass energies of its nucleons minus the rest mass energy of the nucleus. (d) It is the sum of the kinetic energy of all the nucleons in the nucleus.
Answer» (d) It is the sum of the kinetic energy of all the nucleons in the nucleus.

Discussion

24.	An α-particle is bombarded on 14N. As a result, a 17O nucleus is formed and a particle is emitted. This particle is a(a) neutron (b) proton (c) electron (d) positron.
Answer» (b) This particle is a proton.

Discussion

Explore topic-wise InterviewSolutions in .

As the mass number A increases, which of the following quantities related to a nucleus do not change?(a) mass (b) volume (c) density (d) binding energy.

A freshly prepared radioactive source of half-life 2h 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) 6h (b) 12h (c) 24h (d) 128h.

During a negative beta decay, (a) an atomic electron is ejected (b) an electron which is already present within the nucleus is ejected (c) a neutron in the nucleus decays emitting an electron(d) a proton in the nucleus decays emitting an electron.

The decay constant of a radioactive sample is X. The half-life and the average-life of the sample are respectively(a) 1/λ and (In 2/λ) (b) (In 2/λ) and 1/λ(c) λ(ln 2) and 1/λ (d) λ/(ln 2) and 1/λ.

In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following particles is emitted in the decay? (a) proton (b) neutron (c) electron (d) photon.

The masses of 11C and 11B are respectively 11.0114 u and 11.0093 u. Find the maximum energy a positron can have in the β+-decay of 11C to 11B.

How much energy is released in the following reaction?7Li+p→α+αAtomic mass of 7Li - 7.0160 u and that of 4He - 4.0026 u.

As the mass number A increases, the binding energy per nucleon in a nucleus(a) increases (b) decreases (c) remains the same (d) varies in a way that depends on the actual value of A.

Find the binding energy per nucleon of (197,79)Au if its atomic mass is 196.96 u.

In which of the following decays the element does not change?(a) α-decay (b) β -decay (c) β -decay (d) γ-decay.

Which of the following are electromagnetic waves? (a) α -rays (b) beta-plus rays(c) beta-minus rays (d) gamma rays.

Magnetic field does not cause deflection in (a) α-rays (b) beta-plus rays (c) beta-minus rays (d) gamma rays.

During a nuclear fission reaction, (a) a heavy nucleus breaks into two fragments by itself (b) a light nucleus bombarded by thermal neutrons breaks up (c) a heavy nucleus bombarded by thermal neutrons breaks up (d) two light nuclei combine to give a heavier nucleus and possibly other products.

The graph of In(R/R0) versus In A (R = radius of a nucleus and A = its mass number) is(a) a straight line (b) a parabola(c) an ellipse (d) none of them.

The mass number of a nucleus is(a) always less than its atomic number(b) always more than its atomic number(c) equal to its atomic number(d) sometimes more than and sometimes equal to its atomic number.

Two protons are kept at a separation of 10nm. Let Fn and Fe be the nuclear force and the electromagnetic force between them.(a )Fe = Fn (b)Fe &gt;&gt; Fn (c )Fe &lt;&lt; Fn(d) Fe and Fn differ only slightly.

As compared to 12C atom, 14C atom has(a) two extra protons and two extra electrons(b) two extra protons but no extra electron(c) two extra neutrons and no extra electron(d) two extra neutrons and two extra electrons.

The mass number of a nucleus is equal to(a) the number of neutrons in the nucleus(b) the number of protons in the nucleus(c) the number of nucleons in the nucleus(d) none of them.

The mass of a neutral carbon atom in ground state is (a) exact 12u (b) less than 12u(c) more than 12u(d) depends on the form of carbon such as graphite or charcoal.

In one average-life,(a) half the active nuclei decay(b) less than half the active nuclei decay(c) more than half the active nuclei decay(d) all the nuclei decay.

An α-particle is bombarded on 14N. As a result, a 17O nucleus is formed and a particle is emitted. This particle is a(a) neutron (b) proton (c) electron (d) positron.

Two protons are kept at a separation of 10nm. Let Fn and Fe be the nuclear force and the electromagnetic force between them.(a )Fe = Fn (b)Fe >> Fn (c )Fe << Fn(d) Fe and Fn differ only slightly.