IB PHYSICS
HL Option J – Particle Physics
Assignment
1.
This question is about a proton.
The proton particle is made out of three quarks.
(a)
Explain why the three quarks in the proton do not violate the Pauli exclusion principle.
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(2)
(b)
Quarks have spin
1
2
. Explain how it is possible for the proton to also have spin
1
.
2
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(2)
(Total 4 marks)
2.
(a)
Outline
(i)
what is meant by a deep inelastic scattering experiment.
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(2)
(ii)
how deep inelastic scattering experiments give evidence in support of the existence
of quarks and gluons.
quarks:
.......................................................................................................
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gluons:
.......................................................................................................
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(4)
(b) Deep inelastic scattering experiments indicate that the quarks inside hadrons behave as free
particles. Suggest a reason for this.
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(2)
1
(c)
State two fundamental differences between the standard model for quarks and leptons and
the theory of strings.
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(2)
(Total 10 marks)
3.
This question is about fundamental particles.
Particle production and annihilation are subject to conservation laws. Two of these laws are
conservation of mass-energy and conservation of momentum.
(a)
State the names of three other conservation laws.
1.
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2.
.........................................................................................................................
3.
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(3)
(b) Free neutrons are unstable. A neutron may decay to become a proton with the emission of
an electron. A student represents the decay by the following equation.
1
1
0 n 1
(i)
p  10e
State, by reference to conservation laws, why the student’s equation is not correct.
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(1)
(ii)
Write down the correct decay equation.
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(1)
(Total 5 marks)
4.
This question is about the decay of a neutron.
The diagram below illustrates a neutron decaying into a proton by emitting a −-particle.
proton
particle X
-particle
particle Y
neutron
2
State the name of
(a)
the force involved in this decay;
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(1)
(b)
the particle X;
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(1)
(c)
the exchange particle Y involved in the decay.
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(1)
(Total 3 marks)
5.
This question is about radioactive decay.
The decay process of a neutron is given by the following equation.
n  p  e  ve
(a)
Complete the table below.
particle
n
p
e–
ve
baryon number
lepton number
(2)
(b)
Baryon number and lepton number are both conserved in this decay process. State one
other property that is conserved.
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(1)
(Total 3 marks)
3