2024年5月5日发(作者：)
Section3 particle physics
1． The nuclear atom
(1) Mass number and atomic number
(2) Alpha particle scattering experiment
(3) Electrons are accelerated by E and B
(4) Write equations using standard nuclear notating
(5)Explain why high energies are required to break particles into their constituents
and to investigate fine structure
(6) de Broglie wavelength λ=h/p
(201306R-7)The de Broglie wavelength associated with electrons moving at 2.5 × 10
6
m s
–1
is
A .2.9 × 10
–4
m B .2.4 × 10
–8
m C .2.9 × 10
–10
m D .2.4 × 10
–39
m
(201306-10) The de Broglie wavelength for neutrons used to study crystal structure is
1.2 nm. mass of a neutron = 1.67 × 10
–27
kg
The speed of these neutrons would be
A .3.0 × 10
6
m s
–1
B.3.3 × 10
2
m s
–1
C.3.0 × 10
–3
m s
–1
D.3.3 × 10
–7
m s
–1
(201306R-8 )Which of the following is not a valid conclusion from Rutherford’s
alpha particle scattering experiment?
A .The atom is mainly empty space.
B .The mass of the atom is mostly concentrated in the nucleus.
C. The nucleus must be positively charged.
D .The nucleus must be very small compared to the atom.
(201306R-9) Select the row in the table that correctly identifies the composition of a
235+
92
U ion.
Number of protons Number of neutrons Number of electrons
A 92 143 91
B 92 143 92
C 92 235 91
D 93 235 92
(201306-1)The nucleus of one of the isotopes of nickel is represented by
60
28
Ni.
Which line correctly identifies a neutral atom of this isotope?
Number of protons Number of neutrons Number of electrons
A 28 32 28
B 28 32 32
C 28 60 28
D 60 28 28
（201201-10） The de Broglie wavelength of a moving tennis ball is calculated as 1 ×
10
-33
m. This means that the moving tennis ball
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A .diffracts through a narrow slit. not behave as a particle.
not display wave properties. travelling at the speed of light.
(201306R-10) .A transmission
electron microscope passes a
beam of electrons through a
tiny specimen to form an image
on a viewing screen
Due to the wave nature of
electrons, diffraction occurs
which can blur the image. To
reduce this effect when
viewing a smaller object the
beam must contain
A .more electrons per second. B .fewer electrons per second.
C. faster moving electrons. D .slower moving electrons
(201306-13).In an experiment to investigate the structureof the atom, α-particles are
fired at a thin metal foil, which causes the α-particles to scatter.
(a) (i) State the direction in which thenumber of α-particles detected will be a
maximum
(ii) State what this suggests about the structure of the atoms in the metal foil.
(b) Some α-particles are scattered through 180°.
State what this suggests about the structure of the atoms in the metal foil.
(c) The diagram shows the path of an α-particle passing near to a single nucleus in
the metal foil.
(i)Name the force that causes
the deflection of the α-particle.
(ii) On the diagram, draw an
arrow to show the direction of
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the force acting on the α-particle at the point where the force is a maximum.
Label the force F.
(iii) The foil is replaced by a metal of greater proton number.
Draw the path of an α-particle that has the same initial starting point and velocity as
the one drawn in the diagram.
(201301-11) Early in the twentieth century physicists observed the scattering of alpha
particles after they had passed through a thin gold foil. This scattering experiment
provided evidence for the structure of the atom.
(a) State why it is necessary to remove the air from the apparatus that is used for this
experiment.
(b) From the results of such an experiment give two conclusions that can be deduced
about the nucleus of an atom.
Conclusion 1
Conclusion 2
(c) The diagram shows three α-particles ,all
with the same kinetic energy .The path followed
by one of the particles is shown . Add to the
diagram to show the paths followed by the other
two particles.
(201302-12 )The electron in a hydrogen atom can be described by a stationary wave
which is confined within the means that the de Broglie wavelength
associated with it must be similar to the size of the atom which is of the order of 10
–10
m.
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(a)(i)Calculate the speed of an electron whose de Broglie wavelength is1.00 × 10
–10
m.
(ii) Calculate the kinetic energy of this electron in electronvolts
(b)When βradiation was first discovered ,it was suggested that there were electrons
in the atomic nucleus, but it was soon realised that this was impossible because the
energy of such an electron would be too great.
Suggest why an electron confined within a nucleus would have a much greater
energy than the energy calculated in (a)(ii).
2． high-energy collisions
(1) The role of E in linear particle accelerators
(2) r=p/BQ in B
(3) ⊿E=c
2
⊿m
(4) Units:MeV,GeV,MeV/c
2
,GeV/c
2
,u
(201301-10)The tubes of a linear accelerator (linac) get progressively longer down its
length because
A .the accelerating particles become relativistic.
B .the frequency of the applied potential difference changes.
C .the accelerating particles must spend the same time in each tube.
D .the accelerating particles gain mass
（201206-10）As a particle accelerates in a linac, it passes through drift tubes of
increasing lengths. This is so that
particle can be given more energy within each tube.
frequency of the accelerating voltage can be constant.
accelerating voltage can be as high as possible.
time spent in the tube by the particle is longer
(201306R-6)Charged particles are travelling at a speed v, at right angles to a magnetic
field of flux density B. Each particle has a mass m and a charge Q.
Which of the following changes would cause a decrease in the radius of the circular
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path of the particles?
A .an increase in B B .an increase in m C .an increase in v D .a decrease in Q
(201306-6) A muon has a mass of 106 MeV/c
2
. The mass of a muon, to two
significant figures, is
A .1.7 × 10
–11
kg B .5.7 × 10
–20
kg C .1.9 × 10
–28
kg D.1.9 × 10
–34
kg
(201201-7)The rest mass of a proton is 1.67 × 10–27 kg. This mass, in MeV/c2 is
approximately
A .2.4 × 10
–20
B.3.1 × 10
–6
C.1.0 D .940
(201106-10) The Large Hadron Collider is designed to accelerate protons to very high
energies for particle physics experiments. Very high energies are required to
A .annihilate hadrons. e hadrons.
C .create particles with large mass. e individual quarks
(201206-13) An electron and a positron annihilate with the emission of two photons
of equal energy. Calculate the wavelength of the photons.
(201201-17) (d) The technology suggested in the science fiction series, Star Trek, for
powering the Starship Enterprise relied on antimatter. When an anti-hydrogen atom
meets a hydrogen atom, they annihilate and produce energy.
(i) How much energy, in joules, would be produced by the annihilation of
just 1 milligram of anti-hydrogen atoms?
(ii) Anti-protons are required to produce anti-hydrogen atoms. The total production of
anti-protons on Earth over the past 25 years adds up to only a few nanograms.
Suggest why so little anti-matter has been created
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3. Particle accelerators
(1) E and B in cyclotron particle accelerators
(2) Relativistic effects at speeds near c
(201306-9)A cyclotron is a type of particle accelerator. It consists of two metal Dees
which are connected to a high frequency voltage supply and are in a strong magnetic
field. The particles change their speed because
the magnetic field they are in.
voltage supply is alternating.
is a potential difference between the two Dees.
magnetic field is at right angles to the Dees.
(201306R-11)*11 The diagram shows the basic structure of a cyclotron.
With reference to the magnetic field and the alternating potential difference explain
how the cyclotron produces a beam of high speed particles.
4. Particle theory
(1) E and B in particle detectors
(2) Charge energy and momentum are conserved in interactions between particles and
hence interpret records of particle tracks
(3) In the standard quark-lepton model each particle has a corresponding anti-particle
meson:quark-anti-quark pairs baryon :quark triplets
(4) Write and interpret equations using Standard symbols
6
(201206-9)A pion can decay to produce two leptons. Which one of the following is
possible?
A.π
+
→e
+
+ v
e
B .π
0
→e– + v
e
C.π
+
→e
+
+ e
–
D π
0
→π
+
+ e
–
(201201-8)A positive kaon (K+) is a meson which includes a strange quark. Its
structure could be
A . u
s
B. us C.
s
dd
D .usd
(201201-9) The K+ is likely to decay to
A.π
+
+ μ
–
+
v
μ
B. π
+
+π
0
Cπ
+
+π
–
D π
0
+ μ
–
+
v
μ
(201306-7 )The diagram shows the tracks from an event at a point P in a bubble
chamber. A magnetic field is directed into the page. The tracks cannot show the
production of a proton-antiproton pair with equal kinetic energies because
A .the curvature is perpendicular to the magnetic field.
B .the tracks curve in different directions.
C. the tracks have different curvatures.
D .there is no track before point P
(201306-11)
Scientists studying anti-matter recently observed the creation of a
nucleus of anti-helium 4, which consists of two anti-protons and two anti-neutrons.
The diagram represents the path of a proton through a magnetic field starting at point
X.
Add to the diagram the path of an anti-helium 4 nucleus also starting
at point X and initially travelling at the same velocity as the
n any differences between the paths.
(201306-14)
The photograph shows tracks in a particle detector.
(a) Explain the role of a magnetic field in a particle
detector
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(b) Explain how you can tell that track XY was produced by a particle moving from
X to Y rather than from Y to X.
(c)The particle that produced track XY was a π+. Deduce the direction of the
magnetic field in the photograph
(d) At Y, the π+ decayed into a positively charged muon (μ+) and a muon neutrino.
The μ+ has a very short range before decaying into various particles, including a
positron which produced the final spiral.
(i) Give two reasons why you can deduce that the muon neutrino is neutral.
(ii) Explain the evidence from the photograph for the production of the muon neutrino
at Y.
(201306R-14) .Hadrons are a group of particles composed of quarks. Hadrons can
be either baryons or mesons.
(a) (i) State the quark structure of a baryon.
(ii) State the quark structure of a meson.
(b) State one similarity and one difference between a particle and its antiparticle.
Similarity:
Difference :
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(c) (i) The table gives some of the properties of up, down and strange quarks.
Type of quark Charge/e Strangeness
u +2/3 0
d -1/3 0
s -1/3 -1
One or more of these quarks combine to form a Κ
+
, a meson with a strangeness of
+1
.
Write down the quark combination of the Κ
+
.
.
(ii) The Κ
+
can decay in the following way Κ
+
→ µ
+
+ v
µ
K
–
is the antiparticle of the K
+
. Complete the equation below by changing each
particle to its corresponding antiparticle in order to show an allowed decay for the
K
–
meson.
Κ
－
→
(iii) The rest mass of the Κ
+
is 494 MeV/c
2
Calculate, in joules, how much energy is released if a Κ
+
meets and annihilates a K
–
(201306-12) The table gives some of the properties of the up, down and strange
quarks.
Type of quark Charge/e Strangeness
u +2/3 0
d -1/3 0
s -1/3 -1
There are nine possible ways of combining u, d and s quarks and their antiquarks to
make nine different mesons. These are listed below
u
u
u
d
u
s
d
d
d
u
d
s
s
s
s
u
s
d
(a) From the list select the four strange mesons and state the charge and strangeness of
each of them.
Meson Charge/e Strangeness
(b) Some of the mesons in the list have zero charge and zero strangeness.
Suggest what might distinguish these mesons from each other.
*14 A bubble chamber is a particle detector which makes use of electric and magnetic
fields. Explain the role of electric and magnetic fields in a particle detector.
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(201301-17)In 2011 physicists at the Relativistic Heavy Ion Collider (RHIC)
announced the creation of nuclei of anti-helium-4 which consists of anti-protons and
anti-neutrons instead of protons and neutrons
(a) ‘Ordinary’ helium-4 is written as
42
do the numbers 4 and 2 represent?
(b) In the RHIC experiment, nuclei of gold
197
79
Au travelling at speeds greater than
2.99 × 108m s
–1
, in opposite directions, collided, releasing energies of up to 200 GeV.
After billions of collisions, 18 anti-helium nuclei had been detected.
(i) What is meant by ‘relativistic’ in the collider’s name?
(ii) State why it is necessary to use very high energies in experiments such as these.
(iii) Show that the mass of a stationary anti-helium nucleus is about 4 GeV/c
2
(iv) State why the small number of anti-helium nuclei produced only survive for a
fraction of a second.
(v) A slow moving anti-helium nucleus meets a slow moving helium nucleus. If they
were to combine to produce 2 high energy gamma rays, calculate the frequency of
each gamma ray.
(c) There are two families of hadrons, called baryons and mesons. Baryons such as
protons are made of three quarks.
(i) Describe the structure of a meson
(ii) Up quarks have a charge of +2/3e and down quarks a charge of –1/3e.
Describe the quark composition of anti-protons and anti-neutrons and use this to
deduce the charge on each of these particles.
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（201206-18）18 (a) Physicists were able to confidently predict the existence of a
sixth quark. State why
(b) The mass of the top quark was determined by an experiment. Collisions between
protons and anti-protons occasionally produce two top quarks.
(i) How do the properties of a proton and an anti-proton compare?
(ii) After the collision the two top quarks move in opposite directions with the same
speed. Explain why.
(c) The two top quarks decay rapidly into two muons and four jets of particles.
These can be detected and their momenta measured
The diagram shows an end-on view of the directions of the four jets (J1 to J4) of
particles. The two muons are shown as μ
1
and μ
2
. A muon neutrino is also
produced but cannot be detected, so is not shown. Each momentum is measured in
GeV/c.
(i)Explain why GeV/c is a valid unit for momentum.
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(ii) The vector diagram shown below is not complete. Add to the diagram arrows to
represent the momenta of J3 and J4.
(iii) Complete the diagram to determine the magnitude of the momentum of the muon
neutrino.
(iv) Show that the total energy of all the products of this event is about 300 GeV.
(v) Deduce the mass of a top quark in GeV/c
2
.
(vi) Suggest why it took a long time to find experimental evidence for the top quark.
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