Radioactivity and Nuclear Reactions - Nuclear and Particle Physics - Physics Previous Year Questions

1

2007 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2007

Fission fragments are generally radioactive as

A

they have excess of neutrons.

B

they have excess of protons.

C

they are products of radioactive nuclides.

D

their total kinetic energy is of the order of 200 MeV.

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2

2007 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2007

Half life of a radio-isotope is \( 4 \times 10^8 \) years. If there are \( 10^3 \) radioactive nuclei in a sample today, the number of such nuclei in the sample \( 4 \times 10^8 \) years ago were

A

\(128 \times 10^3 \)

B

\(256 \times 10^3 \)

C

\(512 \times 10^3 \)

D

\(1024 \times 10^3 \)

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3

2007 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2007

Half life of a radio-isotope is \(4 \times 10^8\) years. If there are \(10^3\) radioactive nuclei in a sample today, the number of such nuclei in the sample \(4 \times 10^8\) years ago were

A

\(128 \times 10^3\)

B

\(256 \times 10^3\)

C

\(512 \times 10^3\)

D

\(1024 \times 10^3\)

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4

2007 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2007

The number of alpha particles hitting the target per second is

A

\(0.5 \times 10^{14}\)

B

\(1.0 \times 10^{14}\)

C

\(2.0 \times 10^{20}\)

D

\(4.0 \times 10^{20}\)

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5

2008 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2008

Consider the β-decay of a free neutron at rest in the laboratory. Which of the following configurations of the decay products correspond to the largest energy of the anti-neutrino \(\bar{\nu}\)? (rest mass of electron \(m_e\) = 0.51 MeV/c², rest mass of proton \(m_p\) = 938.27 MeV/c² and rest mass of neutron \(m_n\) = 939.57 MeV/c²)

A

In the laboratory, proton is produced at rest.

B

In the laboratory, momenta of proton, electron and the anti-neutrino all have the same magnitude.

C

In the laboratory, proton and electron fly-off with (nearly) equal and opposite momenta.

D

In the laboratory, electron is produced at rest.

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6

2008 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2008

Using the result of the above problem, answer the following. Which of the following represents approximately the maximum allowed energy of the anti-neutrino \(\bar{\nu}\)?

A

1.3 MeV

B

0.8 MeV

C

0.5 MeV

D

2.0 MeV

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7

2009 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2009

The disintegration energy is defined to be the difference in the rest energy between the initial and final states. Consider the following process : \(_{94}^{240}Pu \rightarrow _{92}^{236}U + _{2}^{4}He\). The emitted α particle has a kinetic energy 5.17 MeV. The value of the disintegration energy is

A

5.26 MeV

B

5.17 MeV

C

5.08 MeV

D

2.59 MeV

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8

2010 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2010

The basic process underlying the neutron \(\beta-\) decay is

A

\(d \rightarrow u + e^- + \bar{\nu}_e\)

B

\(d \rightarrow u + e^-\)

C

\(s \rightarrow u + e^- + \bar{\nu}_e\)

D

\(u \rightarrow d + e^+ + \bar{\nu}_e\)

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9

2011 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2011

In the \(\beta\)-decay of neutron \(n \rightarrow p + e^- + \bar{\nu}_e\), the anti-neutrino \(\bar{\nu}_e\) escapes detection. Its existence is inferred from the measurement of

A

energy distribution of electrons

B

angular distribution of electrons

C

helicity distribution of electrons

D

forward-backward asymmetry of electrons

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10

2013 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2013

The decay process \(n \rightarrow p^+ + e^- + \bar{\nu}_e\) violates

A

baryon number

B

lepton number

C

isospin

D

strangeness

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11

2013 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2013

In the \(\beta\) decay process, the transition \(2^+ \to 3^+\), is

A

allowed both by Fermi and Gamow-Teller selection rule

B

allowed by Fermi and but not by Gamow-Teller selection rule

C

not allowed by Fermi but allowed by Gamow-Teller selection rule

D

not allowed both by Fermi and Gamow-Teller selection rule

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12

2013 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2013

Consider the decay of a pion into a muon and an anti-neutrino $\pi^- \rightarrow \mu^- + \bar{\nu}_\mu$ in the pion rest frame. $m_\pi = 139.6$ MeV/$c^2$, $m_\mu = 105.7$ MeV/$c^2$, $m_\nu \approx 0$ The energy (in MeV) of the emitted neutrino, to the nearest integer is __________.

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13

2014 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2014

A nucleus X undergoes a first forbidden \(\beta\)-decay to a nucleus Y. If the angular momentum (I) and parity (P), denoted by \(I^P\) as \(\frac{1}{2}^+\) for X, which of the following is a possible \(I^P\) value for Y?

A

\(\frac{1}{2}^+\)

B

\(\frac{1}{2}^-\)

C

\(\frac{3}{2}^+\)

D

\(\frac{3}{2}^-\)

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14

2016 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2016

Consider the reaction \( ^{55}_{25}Mn + e^- \rightarrow \ ^{54}_{24}Cr + X \). The particle X is

A

\(\gamma \)

B

\(\nu_e \)

C

\(n \)

D

\(\pi^0 \)

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15

2016 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2016

A particle of rest mass \( M \) is moving along the positive \( x \)-direction. It decays into two photons \( \gamma_1 \) and \( \gamma_2 \) as shown in the figure. The energy of \( \gamma_1 \) is 1 GeV and the energy of \( \gamma_2 \) is 0.82 GeV. The value of \( M \) (in units of \( \text{GeV}/c^2 \)) is ______. (Give your answer upto two decimal places)

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16

2017 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2017

In the nuclear reaction \(^{13}_{6}C + \nu_e \rightarrow ^{13}_{7}N + X\), the particle \(X\) is

A

an electron

B

an anti-electron

C

a muon

D

a pion

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17

2018 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2018

An α particle is emitted by a ²³⁰Th nucleus. Assuming the potential to be purely Coulombic beyond the point of separation, the height of the Coulomb barrier is ______ MeV (up to two decimal places).
(e²/(4πε₀) = 1.44 MeV-fm, r₀ = 1.30 fm)

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18

2019 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2019

A radioactive element X has a half-life of 30 hours. It decays via alpha, beta and gamma emissions with the branching ratio for beta decay being 0.75. The partial half-life for beta decay in unit of hours is __________

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19

2021 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2021

Assume that \(^{13}N (Z = 7)\) undergoes first forbidden \(\beta^+\) decay from its ground state with spin-parity \(J_i^\pi\), to a final state \(J_f^\pi\). The possible values for \(J_i^\pi\) and \(J_f^\pi\), respectively, are

A

\(\frac{1}{2}^-, \frac{5}{2}^+\)

B

\(\frac{1}{2}^+, \frac{5}{2}^+\)

C

\(\frac{1}{2}^-, \frac{1}{2}^-\)

D

\(\frac{1}{2}^+, \frac{1}{2}^-\)

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20

2022 · Physics · Nuclear and Particle Physics · Radioactivity and Nuclear Reactions

Physics (PH) 2022

Match the order of β – decays given in the left column to appropriate clause in the right column. Here X(I^π) and Y(I^π) are nuclei with intrinsic spin I and parity π.

A

1. X(1/2+) → Y(1/2+)	i) First forbidden β-decay
2. X(1/2-) → Y(5/2+)	ii) Second forbidden β-decay
3. X(3+) → Y(0+)	iii) Third forbidden β-decay
4. X(4-) → Y(0+)	iv) Allowed β-decay

B

1 – i, 2 – ii, 3 – iii, 4 – iv

C

1 – iv, 2 – i, 3 – ii, 4 – iii

D

1 – i, 2 – iii, 3 – ii, 4 – iv

E

1 – iv, 2 – ii, 3 – iii, 4 – i

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