Option 1: Particle Physics

1. Option 1: Particle Physics

2. REVISION OF RADIOACTIVITY

3. What is Radioactive Decay? What is Radioactivity? Radioactive Decay is the disintegration of an unstable nucleus with the emission of one or more types of radiation. Who Discovered Radioactivity? Becquerel

4. What is the structure of an alpha-particle? An alpha-particle is a helium nucleus, i.e. a bundle of two protons and two neutrons, emitted from the nucleus of a radioactive atom. An Alpha-Particle

5. is an alpha-particle emitter. Write an equation to represent the decay of Uranium-238. Thorium Uranium Alpha-Particle

6. What is the nature of a beta-particle? A beta-particle is a high-speed electron emitted from the nucleus of a radioactive atom.

7. In Beta Decay, a neutron decays into a proton with the emission of an electron. Write a nuclear equation for this decay.

8. is an beta-particle emitter. Write an equation to represent the decay of Carbon-14.

9. What three quantities are conserved in any Nuclear Reaction? Mass-Energy is conserved. Momentum is conserved. Electric Charge is conserved.

10. The Neutrino When a nucleus undergoes beta decay it appeared that momentum was not conserved. How did Fermi’s theory of radioactive decay resolve this? It proposed the existence of another particle, called the neutrino, , that had the missing momentum.

11. The existence of the Neutrino was proposed in 1930 but it was not detected until 1956. Give two reasons why it is difficult to detect a neutrino? The Neutrino: is uncharged has a very small mass interacts weakly with matter.

13. In Cockroft and Walton’s Experiment: What particles were used to split nuclei? What nuclei did they split? Each time a lithium nucleus was split, what were the products? How were the products detected? Most of the accelerated protons did not split a lithium nucleus. Explain why. Protons. Lithium nuclei. Two alpha-particles. They produced flashes of light (called scintillations) when they struck a zinc sulphide screen. An atom is mainly empty space and most protons did not collide with any nucleus; they just passed straight through.

14. Write a nuclear equation to represent the splitting of a lithium nucleus by a proton as in Cockroft and Walton’s Experiment. Cockroft and Walton’s Experiment was the first experimental confirmation of Einstein’s equation: E  =  m ​c​2​

15. The Cockroft and Walton Linear Accelerator

16. Each particle has its own anti-particle. What is an Anti-Particle? The Anti-Particle of a given particle has the same mass as the given particle. All other properties of the Anti-Particle are the opposite to that of the particle. e.g. If the particle is charged the anti-particle has the same amount of charge but of the opposite sign. The anti-particle also has the opposite spin to its particle.

17. Compare the properties of the Electron with those of its anti-particle, the Positron. The electron and the positron have the same mass. The electron and positron have the same size electric charge. The electron has negative charge; the positron has positive charge. An electron is matter; a positron is anti-matter. The electron and positron have opposite spin.

18. What is Anti-Matter? Anti-Matter is material or matter made up of anti-particles of the particles out of which normal matter is made. The anti-particles have the same mass and a charge of equal size but opposite sign to their corresponding particles. Paul Dirac predicted anti-matter theoretically in the late 1920s

19. The symbols for the proton, neutron and the electron are: p, n and e-. What are the symbols for the anti-proton, the anti-neutron and the anti-electron. Anti-Proton: Anti neutron: Anti-Electron (Positron) e+or

20. What is meant by Pair Production? Pair production is the creating of a particle and its anti-particle from electromagnetic energy (gamma rays).

21. The following reaction represents pair production. Explain how the Principle of Conservation of Electric Charge applies. γ→ e+ + e- The gamma ray has no charge. total charge before reaction is zero. The electron and positron have equal but opposite charges. total charge after reaction is zero. Total charge before and after are the same i.e. charge is conserved

22. An electron positron pair is produced when a high energy gamma ray interacts with matter. Due to their opposite charges the electron and positron spiral in opposite directions in a magnetic field.

23. Centre European pour la Recherche Nucleaire (CERN)

25. In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other. • What reaction occurs? The kinetic energy of the protons is converted into matter in the form of other particles. • Write an equation showing this reaction. p  +  p  +  energy   →   p  +  p  +  additional particles • What happens if the kinetic energy of the colliding protons is increased? More particles and particles of greater masses are produced.

26. What is the “Particle Zoo”? The bewildering array of different particles produced in accelerators, when the energies of the colliding particles were very large, was called the “Particle Zoo”.

27. Particles are classified according to whether they feel the Strong Nuclear Force or not. There are thus two families of particles. Name them. The Leptons and the Hadrons.

28. What is a Lepton? A Lepton is an elementary particle that does not feel the Strong Nuclear Force. A Lepton feels: the Weak Nuclear Force, the Gravitational Force and if it is charged, the Electromagnetic Force.

29. What is a Hadron? A Hadron is a particle that does feel the Strong Nuclear Force. A Hadron feels: the Strong Nuclear Force the Weak Nuclear Force, the Gravitational Force and if it is charged the Electromagnetic Force.

30. A Lepton is an elementary particle that does not feel the Strong Nuclear Force.

31. What is an Elementary Particle? An Elementary Particle is a particle that is not made up of other particles and has no internal structure. Leptons are Elementary Particles.

32. Hadrons are not elementary particles. Hadrons are made up of elementary particles called Quarks and Antiquarks. Hadrons are divided into two families, called the Baryons and the Mesons.

33. What are Mesons? Mesons are hadrons that have masses between that of the electron and the proton.

34. What are Baryons? Baryons are hadrons that have masses greater than or equal to that of the proton.

35. A Hadron is a particle that feels the strong force. Mesons are hadrons that have masses between that of the electron and the proton. Baryons are hadrons that have masses greater than or equal to that of the proton.

36. What are Quarks? Quarks (and Anti-Quarks) are Elementary Particles out of which hadrons (i.e. baryons and mesons) are made. Quarks have an electric charge of:

37. Name the six flavours of quark? Up, Down Strange, Charmed Top, Bottom

39. What is the quark composition of a Baryon? A Baryon is made up of any three quarks (or any three anti-quarks) A proton consists of two up quarks and a down quark.

40. What is the quark composition of a Meson? A Meson is made up of any one quark and any one anti-quark