Syllabus Edition

First teaching 2014

Last exams 2024

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The Structure of Matter (DP IB Physics: SL)

Exam Questions

4 hours45 questions
1a
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3 marks

The Rutherford-Geiger-Marsden Experiment provided evidence for the structure of the atom. The set up consisted of alpha particles being fired at a thin gold foil, with a detector to detect deflected particles.

The diagram shows some of the potential paths taken by the alpha particles.

7-3-q1a-question-diagram-1-sl-sq-easy-phy

Draw lines to connect the correct statements for each path of the alpha particle.

7-3-q1a-question-diagram-2-sl-sq-easy-phy
1b
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5 marks

Since Rutherford's discovery, further discoveries about the nature of matter have been made.

Complete the following sentences with appropriate words or phrases: 

The nucleus is made of ________ and ________, and these themselves are made of the fundamental particles known as ________. Any particle made of these is known as a ________. Another example of a fundamental particle is the ________.

1c
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6 marks

One type of hadron is the K+ meson, which has a strangeness of +1.

(i)
State the quark composition of a meson
[1]
(ii)
State the baryon number of a K+ meson
[1]
(iii)
Show that the quark composition of a K+ meson is u s with bar on top
[4]
1d
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3 marks

Electrons are an example of another type of fundamental particle called a lepton. 

 
(i)
State the charge on a muon.
[1]
(ii)
State the mass of the electron neutrino.
[1]
(iii)
State the fundamental force which leptons do not interact with, but quarks do.
[1]

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2a
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5 marks

The following particles are available:

p space space space space space space n with bar on top space space space space space space mu to the power of plus space space space space space space e to the power of plus space space space space space space gamma

Identify all examples of:

 
(i)
Hadrons.
[1]
(ii)
Leptons.
[1]
(iii)
Antiparticles.
[1]
(iv)
Charged particles.
[1]
(v)
Exchange particles.
[1]

2b
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2 marks

Quarks can combine to give various baryons and mesons. The proton and neutron are the baryons which subsequently make up the nucleus.

State the quark composition of:

 
(i)
A proton.
[1]
(ii)
A neutron.
[1]

2c
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2 marks

The proton has a charge of +1e.

Explain why the proton has this charge by referring to the charge of its constituent quarks.

2d
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6 marks

Protons and neutrons are both examples of baryons. An electron is an example of a lepton

Complete the table below with the correct charge, baryon and lepton numbers for each particle.

 
  Charge Baryon number Lepton number
Proton, p +1 1  
Anti-Neutron, n with bar on top     0
Pion minus, pi to the power of minus −1   0
Photon, gamma 0 0  
Up quark, u plus 2 over 3   0
Electron, e   0  

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3a
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2 marks

The four fundamental forces are mediated through exchange particles.

Define the phrase 'exchange particle'.

3b
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4 marks

Draw lines to match the force with the correct exchange particle:

7-3-q3b-question-sl-sq-easy-phy
3c
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3 marks

Arrange the four fundamental forces in the boxes below the arrow in order of strongest to weakest.

7-3-q3c-question-sl-sq-easy-phy
3d
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1 mark

Feynman diagrams represent particle interactions in the form of a diagram.

The following is a Feynman diagram showing beta−minus decay, with the exchange particle missing.

7-3-q3d-question-sl-sq-easy-phy

Label the correct exchange particle on the diagram.

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4a
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2 marks

State what is meant by the standard model of particle physics.

4b
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3 marks

The standard model describes the fundamental particles that make up other sub-atomic particles.

One method of representing the standard model is as shown in the diagram below.

7-3-q4b-question-sl-sq-easy-phy

Complete the missing information in the boxes in the diagram.

4c
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3 marks

Another more detailed way of showing the standard model is shown below, where the different fundamental particles are arranged on cards:

7-3-q4c-question-sl-sq-easy-phy

By writing a letter in the correct box, identify:

 
(i)
Quarks, with the letter Q
[1]
(ii)
Leptons, with the letter L
[1]
(iii)
Gauge bosons, with the letter B
[1]

4d
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1 mark

The final particle on the standard model diagram in part (b) is the Higgs boson. It was predicted in 1964 and confirmed in 2012.

State what the Higgs boson is responsible for.

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5a
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2 marks

The following Feynman diagram shows a particle interaction.

7-3-q5a-question-sl-sq-easy-phy

Label the axes of the Feynman diagram.

5b
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2 marks

State: 

(i)
The exchange particle in the interaction shown in part (a).
[1]
(ii)
The fundamental force represented by this exchange particle.
[1]
5c
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6 marks

The Feynman diagram in part (a) represents part of the particle interaction

pi to the power of minus plus p rightwards arrow K to the power of 0 plus capital lambda to the power of 0

The composition of each particle in terms of quarks is:

  • pi to the power of minus equals d space u with bar on top
  • p equals u u d
  • K to the power of 0 equals d space s with bar on top
  • capital lambda to the power of 0 equals u d s
 
(i)
Identify the two particles in this interaction which contain a strange or anti-strange quark .
[2]
(ii)
By considering the strangeness of each of the particles, show that strangeness is conserved in this interaction.
[3]
(iii)
State the interaction which does not conserve strangeness.
[1]
5d
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5 marks

Quarks can only exist within hadrons, this is known as quark confinement. 

Complete the gaps in the sentences below to describe confinement:

There are two types of hadron, ________ and ________. Quarks cannot be ________ but must be in pairs or triplets. Quarks are kept in place by ________. If an attempt is made to separate quarks, more ________ are produced using the energy required to separate them.

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1a3 marks

Rutherford used the scattering of α particles to provide evidence for the structure of the atom. The apparatus includes a narrow beam of α particles fired at a very thin sheet of gold foil inside a vacuum chamber.

Explain why it is essential to use:

(i)
a vacuum in the chamber

[1]

(ii)
a very thin sheet of gold foil    

[1]

(iii)
a narrow beam of alpha particles   

[1]

1b3 marks

The diagram shows α particles incident on a layer of atoms in a gold foil.

On the diagram, draw and complete the paths followed by each of the α particles shown.

ma1b_7-3_medium_ib-physics

1c5 marks

Outline the results of the scattering experiment by explaining:

(i)
the main observations of the scattering experiment

[2]

(ii)
the significance of each observation

[3]

1d6 marks

The Thomson model of the atom preceded Rutherford’s model. In the Thomson model, the atom was imagined as a sphere of positive charge of diameter 10–10 m containing electrons moving within the sphere.

Thomson’s model could explain some of the results of the Rutherford experiment, but not all.

Explain

(i)
why, at small deflections, Rutherford’s experiment can be explained by Thomson’s model but not at large deflections

[3]

(ii)
why Rutherford’s model of the atom can account for the results at both small and large deflections

[3]

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2a3 marks

Electron capture is one of the ways a nucleus attains stability.

In this process, a proton in the nucleus ‘captures’ an inner-shell electron. While the mass number is unchanged, the atomic number decreases by 1, and a highly energetic particle is released.

Deduce the type of interaction responsible for this process and explain your reasoning.

2b4 marks

By writing an appropriate equation for this process and applying the laws of particle physics, identify the highly energetic particle emitted in this process.

2c5 marks

At the quark level, only some are directly involved in this process. Those which are not are sometimes called ‘spectator quarks’.

(i)
Use your equation to sketch a suitable Feynman diagram for this process.

[3]

(ii)
Sketch another Feynman diagram in terms of the quarks directly involved in electron capture. Do not include spectator quarks.

[2]

2d2 marks

A similar process known as muon capture is being investigated for use in the disposal of highly radioactive waste. A highly energetic muon beam causes muons to be captured by protons in the nuclei of the radioactive isotopes in order to convert them into more stable isotopes.

Write the equation and sketch a Feynman diagram for this process.

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3a4 marks

Compare and contrast the properties of baryons and mesons.

3b4 marks

straight capital sigma to the power of 0 is a baryon with a quark structure of u d s.

A proposed particle interaction involving the straight capital sigma to the power of 0 baryon is:

                   space p plus e to the power of plus rightwards arrow e to the power of minus plus capital sigma to the power of 0 plus K to the power of plus

Use the principles of conservation of charge, baryon number, lepton number and strangeness to determine whether this decay is possible.

3c3 marks

straight capital sigma to the power of 0 is part of a family of baryons called Sigma baryons. They are all strange particles.

Determine the quark combination of the straight capital sigma to the power of plus baryon. Clearly show your working

3d4 marks

Determine the charge, baryon number, lepton number and strangeness of a particle with the quark combination d d s.

Clearly explain your reasoning for each.

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4a2 marks

The virtual photon mediates the electromagnetic force.

It is called a ‘virtual’ photon because it is not detectable in a laboratory.

Sketch a Feynman diagram to show electrostatic repulsion between two electrons.

4b3 marks

Explain why virtual photons cannot be detected in a laboratory but are nonetheless required by particle physics.  

4c3 marks

The unfinished Feynman diagram shows the interaction between a proton and an anti-neutrino. 
q4c_7-3_medium_ib-physics-1

Complete the Feynman diagram.

4d3 marks

The neutron-neutrino interaction can be expressed in a similar way to the Feynman diagram in part (c).

Describe the changes to the Feynman diagram in part (c) that would show the neutron-neutrino interaction.

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5a2 marks

The Feynmann diagrams show two electroweak interactions between electrons. One of the exchange particles is a photon.

 q5a_the-structure-of-atom_ib-sl-physics-sq-medium-3

 

(i)
Identify the other exchange particle which isn’t a photon

[1]

(ii)
Outline one difference between the two exchange particles

[1]

5b2 marks

Outline how interactions in particle physics are understood in terms of exchange particles.

5c2 marks

Describe the significance of the Higgs Boson in the standard model of quarks and leptons.

5d3 marks

The discovery of the Higgs Boson marked a huge accomplishment for particle physicists.

It was first hypothesised by Peter Higgs and his team in 1964 and then discovered by a large collaborative effort at the CERN particle physics laboratory much later in 2012.

Explain what is meant by the term ‘hypothesised’ and suggest why it took over forty years to discover the Higgs Boson.

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1a
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3 marks

Particle X has a strangeness of –1 and decays to produce a proton and a pion.

X space rightwards arrow space p space plus space straight pi to the power of –

Deduce the quark structure of particle X.

1b
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3 marks

A strange quark decays in the following way

s rightwards arrow u space plus thin space Y space plus space d

Deduce particle Y.

1c
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3 marks

Hence, draw a Feynman diagram at the quark level for the decay of particle X.

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2a
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3 marks

Explain why the discovery of the Higgs Boson was of crucial significance.

2b
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3 marks

Draw a Feynman diagram for the interaction

e to the power of minus plus e to the power of plus rightwards arrow d plus d with bar on top

Assume that the time axis is from left to right.

2c
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3 marks

Explain why multiple hadrons have been produced in this reaction.

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3a
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3 marks

A young student of physics reads up about particles and anti-particles.

In their physics lesson, they excitedly tell their teacher how they learned that a proton has an anti-particle called an anti-proton, and the neutron has an anti-particle called an anti-neutron.

They go on to say that, since the neutron is neutrally charged, it is its own anti-particle.

Identify the student’s misconception and explain why they are incorrect.

3b
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2 marks

Suggest another particle which is an example of being its own anti-particle and explain your reasoning.

3c
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3 marks

Interactions between protons and neutrons can temporarily violate conservation laws.

qu4c-fig-1

One such interaction is shown.

(i)
Identify the type of interaction shown.
[1]
(ii)
By referencing the properties of the exchange particle, explain how it temporarily violates conservation laws.
[2]

 

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4a
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4 marks

The baryon decuplet is a vision tool used by particle physicists to classify groups of particles called baryons.

Discuss the properties of baryons.

4b
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3 marks

In the baryon decuplet, strangeness S is plotted on the horizontal axes and charge Q is plotted on the diagonal axe. Some information is missing.

 

qu2a-fig-1-aqa-sq-hard-physics

Deduce the quark composition of the Ω baryon, using each axis to justify your answer.

4c
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4 marks

Deduce the quark composition and an appropriate symbol for the missing baryon.

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5a
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3 marks
i)
State two particles that are their own antiparticle.

[2]

ii)
Explain why K0 is not its own antiparticle.

[1]

5b
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3 marks

The K0 meson decays into two pions and has a strangeness of 1. State the decay equation at the quark level for the K0 meson.

5c
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4 marks

Heavier quarks can decay into lighter quarks by exchanging a virtual particle that meditates the type of interaction. This particle can then decay into a quark and its equivalent anti–quark.

Draw a Feynman diagram for the decay of the Kmeson at the quark level. Clearly label the Kmeson and the two pions.

5d
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4 marks

Muons decay via the same interaction as the K0 meson into leptons. One such decay is

mu to the power of minus rightwards arrow e to the power of minus plus stack nu subscript e with bar on top plus space _ _ _ _

(i)
Complete the missing particle in the decay.
[1]
(ii)
Draw the Feynman diagram for the decay of a negative muon, (μ). Clearly label the time axis.
[3]

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