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Leaving Cert Physics long questions on Particle Physics

2011 Question 10 (a)

(i) List three quantities that are conserved in nuclear reactions.

(ii) Write an equation for a nucleus undergoing beta-decay.

(iii)In initial observations of beta-decay, not all three quantities appear to be conserved.

What was the solution to this contradiction?

(iv) List the fundamental forces of nature in increasing order of their strength.

(v) Which fundamental force of nature is involved in beta-decay?

(vi) In the Large Hadron Collider, two protons with the same energy and travelling in opposite

directions collide. Two protons and two charged pi mesons are produced in the collision.

Why are new particles produced in the collision?

(vii) Write an equation to represent the collision.

(viii) Show that the kinetic energy of each incident proton must be at least 140 MeV for the

collision to occur.

2010 Question 10 (a)

(i) What is anti-matter?

(ii) An anti-matter particle was first discovered during the study of cosmic rays in 1932.

Name the anti-particle and give its symbol.

(iii)What happens when a particle meets its anti-particle?

(iv) What is meant by pair production?

(v) A photon of frequency 3.6 × 1020 Hz causes pair production.

Calculate the kinetic energy of one of the particles produced, each of which has a rest mass

of 9.1 × 10–31 kg.

(vi) A member of a meson family consists of two particles. Each particle is composed of up and

down quarks and their anti-particles.

Construct the possible combinations. Deduce the charge of each combination and identify

each combination.

(vii) What famous Irish writer first thought up the name ‘quark’?

2009 Question 10 (a)

In 1932 Cockcroft and Walton succeeded in splitting lithium nuclei by bombarding them with

artificially accelerated protons using a linear accelerator.

Each time a lithium nucleus was split a pair of alpha particles was produced.

(i) How were the protons accelerated?

(ii) How were the alpha particles detected?

(iii) Write a nuclear equation to represent the splitting of a lithium nucleus by a proton.

(iv) Calculate the energy released in this reaction.

(v) Most of the accelerated protons did not split a lithium nucleus. Explain why.

Cockcroft and Walton’s apparatus is now displayed at CERN in Switzerland, where very high

energy protons are used in the Large Hadron Collider.

In the Large Hadron Collider, two beams of protons are accelerated to high energies in a circular

accelerator. The two beams of protons then collide producing new particles. Each proton in the

beams has a kinetic energy of 2.0 GeV.

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Leaving Cert Physics long questions on Particle Physics 2011 Question 10 ( a ) (i) List three quantities that are conserved in nuclear reactions. (ii) Write an equation for a nucleus undergoing beta-decay. (iii)In initial observations of beta-decay, not all three quantities appear to be conserved. What was the solution to this contradiction? (iv) List the fundamental forces of nature in increasing order of their strength. (v) Which fundamental force of nature is involved in beta-decay? (vi) In the Large Hadron Collider, two protons with the same energy and travelling in opposite directions collide. Two protons and two charged pi mesons are produced in the collision. Why are new particles produced in the collision? (vii) Write an equation to represent the collision. (viii) Show that the kinetic energy of each incident proton must be at least 140 MeV for the collision to occur.

2010 Question 10 (a) (i) What is anti-matter? (ii) An anti-matter particle was first discovered during the study of cosmic rays in 1932. Name the anti-particle and give its symbol. (iii)What happens when a particle meets its anti-particle? (iv) What is meant by pair production? (v) A photon of frequency 3.6 × 10^20 Hz causes pair production. Calculate the kinetic energy of one of the particles produced, each of which has a rest mass of 9.1 × 10–31^ kg. (vi) A member of a meson family consists of two particles. Each particle is composed of up and down quarks and their anti-particles. Construct the possible combinations. Deduce the charge of each combination and identify each combination. (vii) What famous Irish writer first thought up the name ‘quark’?

2009 Question 10 (a) In 1932 Cockcroft and Walton succeeded in splitting lithium nuclei by bombarding them with artificially accelerated protons using a linear accelerator. Each time a lithium nucleus was split a pair of alpha particles was produced. (i) How were the protons accelerated? (ii) How were the alpha particles detected? (iii) Write a nuclear equation to represent the splitting of a lithium nucleus by a proton. (iv) Calculate the energy released in this reaction. (v) Most of the accelerated protons did not split a lithium nucleus. Explain why.

Cockcroft and Walton’s apparatus is now displayed at CERN in Switzerland, where very high energy protons are used in the Large Hadron Collider. In the Large Hadron Collider, two beams of protons are accelerated to high energies in a circular accelerator. The two beams of protons then collide producing new particles. Each proton in the beams has a kinetic energy of 2.0 GeV.

(vi) Explain why new particles are formed. (vii) What is the maximum net mass of the new particles created per collision? (viii)What is the advantage of using circular particle accelerators in particle physics?

(mass of alpha particle = 6.6447 × 10–27^ kg; mass of proton = 1.6726 × 10–27^ kg; mass of lithium nucleus = 1.1646 × 10–26^ kg; speed of light = 2.9979 × 10^8 m s–1; charge on electron = 1.6022 × 10–19^ C) 2008 Question 10 part (a) Baryons and mesons are made up of quarks and experience the four fundamental forces of nature. (i) List the four fundamental forces and state the range of each one. (ii) Name the three positively charged quarks. (iii)What is the difference in the quark composition of a baryon and a meson? (iv) What is the quark composition of the proton? (v) In a circular accelerator, two protons, each with a kinetic energy of 1 GeV, travelling in opposite directions, collide. After the collision two protons and three pions are emitted. What is the net charge of the three pions? Justify your answer. (vi) Calculate the combined kinetic energy of the particles after the collision; (vii) Calculate the maximum number of pions that could have been created during the collision.

(charge on electron = 1.6022 × 10–19^ C; mass of proton = 1.6726 × 10–27^ kg; mass of pion = 2.4842 × 10–28^ kg; speed of light = 2.9979 × 10^8 m s–1)

2007 Question 10 (a) Read the following passage and answer the accompanying questions. Ernest Walton was one of the legendary pioneers who made 1932 the annus mirabilis of experimental nuclear physics. In that year James Chadwick discovered the neutron; Carl Anderson discovered the positron; Fermi articulated his theory of radioactive decay; and Ernest Walton and John Cockcroft split the nucleus by artificial means. In their pioneering experiment Cockcroft and Walton bombarded lithium nuclei with high-energy protons linearly accelerated across a high potential difference (c. 700 kV). The subsequent disintegration of each lithium nucleus yielded two helium nuclei and energy. Their work gained them the Nobel Prize in 1951. (Adapted from “Ernest Thomas Sinton Walton 1903 –1995 The Irish Scientist” McBrierty; 2003) (i) Draw a labelled diagram to show how Cockcroft and Walton accelerated the protons. (ii) What is the velocity of a proton when it is accelerated from rest through a potential difference of 700 kV? (iii)Write a nuclear equation to represent the disintegration of a lithium nucleus when bombarded with a proton. (iv) Calculate the energy released in this disintegration. (v) Compare the properties of an electron with that of a positron. (vi) What happens when an electron meets a positron? (vii) In beta decay it appeared that momentum was not conserved. How did Fermi’s theory of radioactive decay resolve this? charge on electron = 1.6022 × 10–19^ C; mass of proton = 1.6726 × 10–27^ kg;

(vii) In an accelerator, two high-speed protons collide and a series of new particles are produced, in addition to the two original protons. Explain why new particles are produced. (viii) A huge collection of new particles was produced using circular accelerators. The quark model was proposed to put order on the new particles. List the six flavours of quark. (ix) Give the quark composition of the proton. (Refer to Mathematics Tables, p. 44.)

2004 Question 10 (a) (i) Beta decay is associated with the weak nuclear force. List two other fundamental forces of nature and give one property of each force. (ii) In beta decay, a neutron decays into a proton with the emission of an electron. Write a nuclear equation for this decay. Calculate the energy released during the decay of a neutron. (iii)Momentum and energy do not appear to be conserved in beta decay. Explain how the existence of the neutrino, which was first named by Enrico Fermi, resolved this.

During the late 1930s, Fermi continued to work on the nucleus. His work led to the creation of the first nuclear fission reactor in Chicago during 1942. The reactor consisted of a ‘pile’ of graphite moderator, uranium fuel with cadmium control rods.

(iv) What is nuclear fission? (v) What is the function of the moderator in the reactor? (vi) How did the cadmium rods control the rate of fission? mass of neutron = 1.6749 × 10–27^ kg; mass of proton = 1.6726 × 10–27^ kg; mass of electron = 9.1094 × 10–31^ kg; speed of light = 2.9979 × 10^8 m s–

2003 Question 10 (a) (i) Leptons, baryons and mesons belong to the “particle zoo”. Give (i) an example, (ii) a property, of each of these particles. (ii) The following raction represents pair production. γ → e+^ + e– Calculate the minimum frequency of the γ-ray photon required for this reaction to occur. (iii)What is the effect on the products of the reaction if the frequency of the γ-ray photon exceeds the minimum value? (iv) The reverse of the above reaction is known as pair annihilation. Write a reaction that represents pair annihilation. (v) Explain how the principle of conservation of charge and the principle of conservation of momentum apply in pair annihilation. mass of electron = 9.1 × 10–31^ kg; speed of light, c = 3.0 × 10^8 m s–1^ ; Planck constant, h = 6.6 × 10 –34^ J s

2002 Question 10 (a) (i) Name the four fundamental forces of nature. (ii) Which force is responsible for binding the nucleus of an atom? (iii)Give two properties of this force. (iv) In 1932, Cockcroft and Walton carried out an experiment in which they used high-energy protons to split a lithium nucleus. Outline this experiment. (v) When a lithium nucleus (^7 3 Li) is bombarded with a high-energy proton, two α-particles are produced. Write a nuclear equation to represent this reaction. (vi) Calculate the energy released in this reaction.

mass of proton = 1.6730 × 10-27^ kg; mass of lithium nucleus = 1.1646 × 10-26^ kg; mass of α-particle = 6.6443 × 10-27^ kg; speed of light, c = 3.00 × 10^8 m s-1.

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