P2 - Radioactivity

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  • Created by: EllenMIW
  • Created on: 19-12-15 14:45
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  • Radicoactivity - P2
    • Types of radiation
      • Alpha
        • 2 protons, 2 neutrons (like He nucleus)
        • +2 relative charge
        • Relative mass 4
        • Low penetrating ability
          • Stopped by paper/skin
          • Few centimeters in air
        • Strog ionising ability
        • Deflected by electric field and magnetic field
        • Smoke detector
      • Beta
        • Electron
        • -1 relative charge
        • Negligible relative mass
        • Moderate penetrating ability
          • Stopped by aluminium
          • Several centimeters in air
        • Moderate ionising ability
        • Deflected by electric and magnetic field
        • Thickness gauging
      • Gamma rays
        • Electromagnetic wave
        • 0 relative charge
        • 0 relative mass
        • High penetrating ability
          • Never stopped; reduced by thick lead
        • Weak ionising ability
        • Not deflected by electric or magnetic field
        • Sterilisation, tracing
    • Background radiation
      • Radiation all around us
      • 42% from radon gas
    • Istopes
      • Different numbers of neutrons
    • Rutherford's experiment
      • Vacuum so alpha could travel
      • Thin gold foil bombarded with alpha
      • Most straight through, some deflected slightly, 1 in 8000 bounced back
        • Only explained by presence of tiny nucleus with most of mass
    • Half life
      • The time it takes for the number of atoms of the isotope to halve
      • Exponential decay curve
    • Activity of a radioactive substance
      • The number of atoms that decay per second
    • Nuclear fission
      • Neutron absorbed, splits into 2 nuclei
        • Large amount of energy released, new atoms are radioactive
          • Gamma radiation and kinetic energy
      • Fission fragments
      • Control rods control reaction
      • Moderator slows neutrons in uranium fueled reactor
      • Uranium -235 or plutonium -239
    • Nuclear fusion
      • 2 hydrogen nuclei collide and fuse to form a helium nucleus
      • Gas in reactor heated by passing electric current through it
        • Forms plasma of small nuclei
          • Contained using magnetic field to stop touching walls
      • Better than fission
        • Short half life of waste
        • No danger of reactor going into meltdown
    • Chernobyl 1986, nuclear reactor explosion
    • Early Universe
      • Cools  as expands
      • Less than 2 mins after big bang, quarks, electrons, protons and neutrons formed
      • After 100,000 years, atoms formed (radiation)
      • A few billion years later, gravity caused galaxies
    • Life of a star
      • Nebula drawn together by gravity into protostar
        • Denser and hotter = nuclear fusion= star
          • Stable as force of gravity = radiation pressure
            • Runs out of hydrogen
              • Stars like Sun
                • Expand and cool to red giant
                  • Heavier elements fused in core
                    • Shrinks and heats to white dwarf
                      • Cools into black dwarf
              • Larger stars
                • Expand to supergiants
                  • Explode in supernova
                    • Core compressed to neutron star or black hole
                    • Forms elements heavier than iron

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