Physics paper 1

• Types of Radiation

  • Man-Made
  • Rocks
  • Cosmic rays
  • Nuclear Radiation
• Nuclear Radiation


  • Arrangement can change with the absorption or emission of EM radiation
• Types of Nuclear Radiation

  • Alpha
  • Beta
  • Gamma
• Alpha Radiation

  2 neutrons and 2 protons (same as helium nucleus)
• Beta Radiation


  High speed electron emitted when a neutron turns into a proton in nucleus
• Gamma Radiation


  Very penetrating, only stopped by a few cm of lead
• Atomic Models


  • Bohr Model
  • Plum Pudding Model
• Plum Pudding Model

  • Ball of positive charge with negative charges scattered throughout
• Bohr Model


  • Central nucleus, electrons in energy levels orbiting it
• Alpha Scattering proves: Nucleus is small and positively charged, Atom mostly empty space
• Protons


  + charge
• Neutrons


  0 charge
• Electrons


  • Charge
• Atomic Number


  Determines how many electrons the atom has
• Mass Number


  Number of protons and neutrons
• Isotopes


  Element with different numbers of neutrons
• Natural nuclear weapons testing and nuclear accidents
• Nuclear Fission


  1. Unstable nuclei must absorb a slow-moving neutron

  2. Splitting of large and unstable nuclei

  3. Produces two smaller nuclei and releases energy

  4. Releases two or three neutrons

  5. Once released, induce further fission
• Nuclear Fusion


  1. Joining of two light nuclei into a larger nucleus

  2. Mass is converted into energy in the form of radiation
• Uses of Nuclear Radiation

  • Destroying Unwanted Tissue
  • Medical Tracers
• Radioactive Decay


  Random, which nuclei and when it will decay is unpredictable
• Activity


  Rate at which a nuclei decays, measured in becquerels (Bq)
• Half-Life


  Time for number of unstable nuclei in a given isotope to halve
• Count-Rate


  Measured using a Geiger-Muller tube
• States of Matter


  • Solids
  • Liquids
  • Gases
• Density


  Mass per unit volume
• Density formula


  ρ = m/v
• Density is measured in kg/m³
• Mass is always conserved in changes of state
• Changes of State


  1. Melting: Solid → Liquid

  2. Evaporation: Liquid → Gas

  3. Condensation: Gas → Liquid

  4. Sublimation: Solid → Gas
• Internal Energy


  The total kinetic and potential energies of the particles in a system
• Solids


  • Particles can only vibrate about fixed positions
• Liquids


  • Particles can flow over each other
• Gases


  • Particles can move freely
• Solids


  Highest Density
• Gases


  Lowest Density
• Solids


  Least Kinetic Energy
• Gases


  Most Kinetic Energy
• Physical Changes


  If change is reversed the material's properties can be recovered
• Chemical Changes


  Cannot easily recover its original properties