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Nuclear and Particle Physics Understand the structure of matter, from the atomic nucleus to fundamental forces. Understand radioactivity, fusion and fission. Nuclear and Particle Physics What does an atom look like and how do we know? Nuclear and Particle Physics Nuclear and Particle Physics Nuclear and Particle Physics Nuclear and Particle Physics What was expected v what actually happened? How big is a nucleus, e.g. gold? The size of the nucleus What is Coulomb’s law? The charge on an alpha particle is +2e The charge on a nucleus is +Ze Nuclear and Particle Physics d = 3.0 x 10-14 m This would be a maximum possible radius for a gold atom In general, radius of an atom is 10-10 m and the nucleus is 10-15 m What prefix would be suitable for nuclear dimensions? Nuclear and Particle Physics Diameter = 22cm Nucleons Nucleons refers to either a proton or a neutron Protons have a charge +e Atomic Mass Units Atomic mass units, u, 1u is one twelfth the mass of a neutral carbon-12 atom 1u = 1.661 x 10-27 kg Compare this to the mass of a proton or neutron in your formula sheet Nucleon Size and Density A gold nucleus is much bigger than a hydrogen nuclear The size of a nucleus depends on the number of nucleons 1 3 R= r0 A Radius of nuclei Nucleon Number 1fm Estimate the density of a nucleus Nuclear and Particle Physics Plot a graph of the radius of the nucleiagainst atomic number (up to 150) Nuclear and Particle Physics The Strong Force How do all the positive protons in a nuclear stay together. They should repel …….. Calculate the force between two protons in a helium nucleus. The Strong Force The gravitational force is not enough to hold the nucleus together The strong force acts between all nucleons Nuclear and Particle Physics The Fundamental Forces Electromagnetic Gravitational Strong Weak Most elementary particle <10-17m Acts On Electric Charge Mass Nuclear Particles Range Infinite Infinite 10-15m Weak Strongest Strength Nuclear and Particle Physics