Cheatography

A-Level Physics - Particles and Radiation Cheat Sheet (DRAFT) by amstoffel

AQA A-Level Physics Topic 2 - Particles and Radiation; made directly in accordance with the AQA 7408 specification

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Consti­tuents of an Atom

 An atom is formed from 3 consti­tuents: protons, neutrons and electrons. Protons and neutrons (called neutrons) are found in the nucleus at the centre Electrons orbit around the nucleus in shells­/energy levels. The diameter of the nucleus is about 1 femtometre (10-15 m) The diamerer of an atom is roughly 100,000 times larger, or 10-10 m Specific charge is the charge­-mass ratio, calculated by dividing a particle's charge by its mass Specific charge (C kg-1) = charge of partic­le/mass of particle

Particle Properties

 Particle Proton Neutron Electron Charge (C) +1.6×10-19 0 -1.6×10-19 Relative Charge +1 0 -1 Mass (kg) 1.67×10-27 1.67×10-27 9.11×10-31 Relative Mass 1 1 0.0005 Specific Charge 9.58×107 0 1.76×1011

Isotopes

 Atoms of the same element always have the same number of protons, and therefore the same atomic number However, they can have different amounts of neutrons, which are called isotopes We can use isotopes for carbon­-da­ting, a method of estimating the age of living organisms like fossils Organisms are made of carbon, which has a radioa­ctive isotope (carbo­n-14) and decays at a known half-life once the organism is dead Therefore we can use the amount of carbon-14 left to determine how old it is by how much carbon remains

Stable and unstable nuclei

 The nucleus is held together by the strong nuclear force (one of 4 fundam­ental forces) It provides an attractive force between nucleons with a range of about 3 femtom­etres ( 3x10-15 m) This overcomes the repulsive electr­ostatic force exerted by positively charged protons on each other At distances less than about 0.5 fm the strong nuclear force is repulsive and prevents the nucleus collapsing into a point

Alpha and beta decay

 Unstable nuclei have too many proton­s/n­eut­ron­s/both, where the SNF is not enough to keep them stable They will often decay via α (alpha) or β- (beta minus) emission in order to become stable, where the type of decay is dependent on the number of each nucleon Alpha decay occurs in large nuclei with too many of both nucleons.Beta-minus decay occurs in neutro­n-rich nuclei.Beta-plus decay occurs in neutro­n-d­efi­cient nuclei. The existence of the neutron was hypoth­esised in the conver­sation of energy law in the beta decay equation

Particles and antipa­rticles

 For every type of particle, there is a corres­ponding antipa­rticle Examples of these include:electron and positronproton and anitprotonneutron and antineutronneutrino and antine­utrino

Comparison of partic­les­/an­tip­art­icles

 Electron (e^-) mass=9.11×10-31 kgrest energy=0.51MeVrelative charge=-1 Positron (e^+)mass=9.11×10-31 kgrest energy=0.51MeVrelative charge=+1 Neutronmass=1.67x10-27 rest energy=940MeVrelative charge=0 Antineutronmass=1.67x10-27 rest energy=940MeVrelative charge=0 Neutrinomass=0relative charge=0 Antineutrinomass=0relative charge=0 In short, particles and their corres­ponding antipa­rticles will have the same mass and rest energy, but different relative charges
The antine­utron and antine­utrino symbols are the same as the particle ones but with a line above them

Photon model of Electr­oma­gnetic (EM) Radiation

 EM Radiation, or light, travels as small packets of energy known as photons Photons transfer energy but have no mass themselves Since EM waves travel at the speed of light and follow Planck's constant, we can use the following equation:Energy of a photon = (Planck's Constant x Speed)­/Wa­vel­ength

Partic­le/­Ant­ipa­rticle intera­ctions

 Pair production is where a photon is converted into an equal amount of matter and antimatterThis only happens when the photon has a energy greater than the total rest energy of both particles, and any excess energy is converted into kinetic energy of the particles. Annihi­lation is where a particle and its corres­ponding antipa­rticle collide, resulting in both of their masses being converted into energy (in the form of 2 photons moving in opposite directions as to conserve momentum).

Fundam­ental Intera­ctions

 There are 4 main fundam­ental forces: strong nuclear, weak nuclear, electr­oma­gnetic and gravity. Forces between particles are caused by exchange particles, which carry energy and momentum between the particles experi­encing the force.Each fundam­ental force has its own exchange particles.

Particle Intera­ctions

 Intera­ction Exchange Particle Range (m) Acts on Strong Gluon/­Pions 3x10-15 Hadrons Weak W boson (both +/-) 10-18 All particles Electr­oma­gnetic Virtual photon (λ) Infinite Charged particles Gravity Graviton (not on spec) Infinite Particles with mass