Solved Examples| Chapter 14 | Particle Physics | Physics 11th | National Book Foundation 2025

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14.1 Find the momentum of a positron, moving with relativistic speed. The energy of the positron is 𝟎.𝟒𝟕𝑴𝒆𝑽.
14.2 Show that the particle reactions given below satisfy the laws of conservation of charge, lepton number and baryon number. (i) 𝝅^−+𝒑=𝝅^𝒐+𝒏+𝝅^−+𝝅^+ (ii) 𝝁^+=𝒆^++𝒗_𝒆+(𝒗_𝝁 ) ̅

14.1 The energy of a particle system is 𝟐𝑴𝒆𝑽 moving with relativistic speed, approach each other. If their masses are 𝟎.𝟓𝟏𝟏𝑴𝒆𝑽/𝒄^𝟐 find their momentum. Also justify why momentum has two values i.e. positive and negative.
14.2 Show that the beta-positive decay and the beta negative decay satisfy the laws of conservation of charge, lepton-number and baryon number.

Q. Encircle the correct option.
Which fundamental conservation principle states that the total number of nucleons (protons and neutrons) remains constant in a closed system?
(a) charge (b) energy (c) nucleon (d) momentum
Charge conservation according to the principle of charge conservation, in any physical process, the total electric charge before and after the process must?
(a) decreases (b) increases (c) become zero (d) becomes neutral
Nucleon exchange in a nuclear reaction, if a nucleus emits an alpha particle (helium nucleus), what happens to the nucleon number (A) of the original nucleus:
(a) decreases by 1 (b) decreases by 2 (c) remains same (d) increases by 1
Charge exchange during beta-minus (β-) decay, a neutron is transformed into a proton, emitting an electron (beta particle) in the process. What happens to the total charge during this decay, the total charge:
(a) increases (b) decreases (c) remains same (d) becomes neutral
Positrons in our atmosphere can be produced during the natural process of?
(a) spinning of earth (b) lightning (c) Earth’s magnetic field (d) winds
Which type of carrier particle has not been found yet?
(a) W-boson (b) Z-boson (c) pion (d) graviton
Which type of hadron is always constructed partially of an anti-quark?
(a) baryon (b) lepton (c) meson (d) photon
Analysis of which particles results into the search of Higgs boson?
(a) W and Z boson (b) Up and Down quark (c) meson and baryons (d) neutrinos & photons
Which device is used for proton decay?
(a) Cyclotron (b) Large Hadron Collider (c) super-kamiokande (d) synchrotron
Lepton number for ‘delta’ particle is:
(a) -1 (b) 0 (c) +1/2 (d) +1
Which particle has baryon number +1?
(a) muon (b) tau (c) kaon (d) omega
The particle which has the color property is:
(a) pion (b) kaon (c) rho (d) proton
Why does beta-minus (β-) decay lead to an increase in the atomic number of the nucleus, while beta-plus (β+) decay results in a decrease in the atomic number?
Explain how the mass-energy equivalence principle, as expressed by Einstein’s famous equation E=mc^2, is relevant to understanding the energy release in nuclear processes such as alpha decay.
How do the principles of nucleon conservation and charge conservation in nuclear reactions reflect deeper symmetries and conservation laws present in the fundamental interactions of subatomic particles?
Can anti-matter burn? Explain.
List at least three applications of anti-matter.
Why are gluons short range exchange particles? Explain.
Why do gluons interact only with particles in the first two rows of the standard model?
What are Feynman diagrams? What information about particles these diagrams give?
What are the differences between quarks and leptons?
What advantages does circular particle accelerators have over the linear particle accelerators?
What is the difference between quantum field theory and the string theory? In general, how do we determine if a particle reaction or decay occurs?
A uranium-238 nucleus undergoes alpha decay, emitting an alpha particle (helium nucleus) with a mass of 4.00151 atomic mass unit (u). Calculate the energy released in this alpha decay process. The speed of light (c) is approximately 3.00×〖10〗^8 meters per second, and 1 atomic mass unit (U) is approximately equal to 931.5MeV/c^2.
A carbon-14 nucleus undergoes beta-minus (β-) decay, emitting a beta particle (electron) with a negligible mass. Calculate the energy released in this beta-minus decay process. The speed of light (c) is approximately 3.00×〖10〗^8 meters per second.
A nucleus undergoes a gamma decay, emitting a gamma ray photon with energy of 2.00MeV. Calculate the frequency and wavelength of this gamma ray.
If the negative solution of Dirac equation is for electron, then prove that the positive solution for same equation is not for a proton of the same momentum.
Show that the following particle reactions satisfy the laws of conservation of charge, lepton-number and baryon-number.
(i) π^-+P=K^++K^-+n (ii) π^+=μ^++v_μ