UITM - Faculty of Applied Science

PHY583 – Test 3 – AS2314D – 20.6.12 - SOLUTIONS

Answer all questions

  1. Describe the four fundamental forces of nature and the field particle that mediates each.

Fundamental forces

Strong force

  • A force that holds nucleus together
  • Short-ranged  1 fm
  • The strongest of the four forces
  • Field particles are gluons

Electromagnetic force

  • Force between charges that holds atoms and molecules together
  • Infinite range
  • Obeys inverse-square law
  • Field particles are photons

Weak force

  • Involved in many decays of nuclear particles which require a change of a quark from one flavor to the onother
  • accounts for the  decay of nuclei & the decay of heavier quarks & leptons.
  • Range  1018 m
  • Its strength is 106 times that of the strong force.
  • Scientists now believe that the weak & electromagnetic forces are two manifestations of a unified force called the electroweak force.
  • Field particles: W, Zo particles

Gravitational force

  • Attractive force between two masses
  • Infinite range
  • The weakest of the four forces 1043 times that of a strong force.
  • Obeys inverse-square law
  • Although this force holds the planets, stars & galaxies together, its effect on elementary particle is negligible.
  • Fields particles are gravitons
  1. State the fundamental interactions responsible for the following decays:

i)Neutral rho meson (0) decays into two pions (+ and ) with half-life of about 1023 s.

Strong force because the half-life is 1020 s.

ii)The neutral kaon (K0) decays into two pions (+ and ) with half-life half-life of about 1010 s.

Weak force because the half-life is  1010 s.

  1. Describe the following process:

An electron positron annihilation process, where an electron and a positron annihilates each other producing two gamma ray photons.

  1. a) List all the fundamental particles known today.

Leptons: electron, electron-neutrino, muon, muon-neutrino, tau, tau-neutrino

Force field carriers: gluons, photons, W, Zo particles

Quarks: up, down,strange, charmed, bottom, top

b) Describe thefollowing terms which provide the classification of particles:

i)bosons

  • Sub-atomic particles that obey Bose-Einstein statistics.
  • Integer spin number
  • No exclusion principle applies
  • E.g. photons, gluons, W, Zo particles
  • Symmetric wave functions

ii)leptons

  • Elementary point-like particles with no structure
  • Currently only six known leptons: electron, muon, tau, (e, ,) and their

respective neutrinos: electron neutrino, muon neutrino and tau neutrino

(e, , , )

  • Spin ½
  • Participate in electromagnetic and weak interactions

iii)Hadrons

  • Particles that interact through the strong force.
  • Two classes of hadrons: mesons (spin 0 or 1) & baryons (spin odd half-integer values
  • Composite particles composed of more elemental units called quarks.

iv)Mesons

  • A type of hadron made up of a quark and an antiquark.
  • All have spin 0 or 1,
  • Their masses between that of the electron & proton.
  • All mesons are known to decay finally into electrons, positrons, neutrinos & photons.
  • Eg. Pion and Kaon

v)Baryons

  • Another type of hadrons, made up of 3 quarks.
  • Their spins are always odd half-integer values .
  • Have masses equal to or greater than the proton
  • E.g. Protons & neutrons
  • With the exception of the proton, all baryons decay in such a way that the end products include a proton.
  1. Determine which of the following reactions can occur. For those that cannot occur, determine the conservation law (or laws) that is violated.

a)

(Baryon number is violated: )

 this reaction cannot occur

b)

Baryon #: Before reaction = 0 After reaction (0)+ (0) = 0 

Lepton #: Before reaction = 0 After reaction (1)+ (+1) = 0 

Strangeness #: Before reaction = 0 After reaction (0) + (0) = 0 

This reaction can occur

c)

Baryon #: Before reaction = 1 After reaction (+1) +(0)+ (0) = 1

Lepton #: Before reaction = 0 After reaction (0) + (+1)+ (1) = 0 

Strangeness #: Before reaction = 0 After reaction (0) + (0)+ (0) = 0 

This reaction can occur

  1. Briefly explainwhat is meant by Quantum Chromodynamics.
  • Quantum Chromodynamics (QCD) is the general theory of how quarks interact with each other.
  • In QCD the color charge carried by each quark is responsible for the strong force between the quarks.
  • Basic color charge interaction: like colors repel, opposite colors attract
  1. a) Explain ITER.
  • Acronym for International Thermonuclear Experimental Reactor
  • The first commercial scale reactor to generate electricity based on nuclear fusion
  • Colaboration between EU, USA, Russia, China, Japan, India, and Republic of Korea
  • Launched in 1985
  • Cadarache in Southern France was selected as the site in 2005
  • Contruction began in 2010
  • Expected completion and began operation in 2020
  • Estimated cost  EUR 20 billion
  • Advantages : no carbon emission

no air pollution

unlimited fuel

intrinsically safe

b)State 3 areas of research and development carried out by Nuclear Malaysia.

  • Medical Technology
  • Water, Waste and Environment
  • Agro Technology
  • Industrial Technology
  • Radiation Technology
  • Nuclear Reactor Technology

c)Should Malaysia resort to nuclear power plant for its future electricity supply? State your stand and provide your arguments.

  • Marks awarded will depend on the strength of facts and arguments.

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