Download PHY583 - Test 3 - 20.6.12 - with solution

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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
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A force that holds nucleus together
Short-ranged  1 fm
The strongest of the four forces
Field particles are gluons
Electromagnetic force
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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
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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
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2.
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.
𝜌0 → + + −
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.
𝐾 0 → + + −
Weak force because the half-life is  1010 s.
3.
Describe the following process:
𝒆− + 𝒆+ ⟶ 𝟐𝜸
An electron positron annihilation process, where an electron and a positron annihilates each
other producing two gamma ray photons.
4.
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
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iii)
Hadrons
 Particles that interact through the strong force.
 Two classes of hadrons: mesons (spin 0 or 1) & baryons (spin odd half-integer
values 𝟏𝟐, 𝟑𝟐, 𝟓𝟐 , . . )
 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.
𝟏 𝟑 𝟓
 Their spins are always odd half-integer values (𝟐 , 𝟐 , 𝟐 , 𝒆𝒕𝒄).
 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.
5.
Determine which of the following reactions can occur. For those that cannot occur,
determine the conservation law (or laws) that is violated.
a)
p + 𝑝 → 𝑝 + 𝜋+
(Baryon number is violated: 1  1  1  0 )
 this reaction cannot occur
b)
      v
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)
n  p  e  ve
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
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6.
Briefly explain what 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
7.
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b)
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c)
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
State 3 areas of research and development carried out by Nuclear Malaysia.
Medical Technology
Water, Waste and Environment
Any 3 or equivalent
Agro Technology
meanings
Industrial Technology
Radiation Technology
Nuclear Reactor Technology
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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