physics p6

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  • Physics
    • ISOTOPES
      • STABLE= e.g carbon 12 (neutrons= 6 protons= 6)
        • UNSTABLE= e.g. Carbon 14 with neutrons=8 protons=6 (RADIOACTIVE) causing it to decay and emit radiation.
    • Decay
      • Radioactive atoms are unstable and they decay to become more stable.
        • When an atom does decay it spits out on or more of the 3 following types of radiation; Alpha, Beta, Gamma
    • Ionisation
      • Where enough energy is transferred to break an atom or molecule into bits called ions. (These can be used for chemical reactions).
    • ALPHA
      • -BIG, HEAVY AND SLOW MOVING
      • Does not penetrate far into materials (stopped quickly).
      • Released by heavy nuclei (e.g. uranium).
      • Has a helium nucleus (2 protons, 2 neutrons) also has a mass of 4 and a charge of 2+
    • ALPHA DECAY
      • Unstable isotope.
        • Wants to become more stable so therefore decays.
          • Loses protons within the process.
            • This therefore changes the element that is decaying and an ALPHA particle is emitted along with a new stable isotope.
    • BETA DECAY
      • They are released by nuclei that have too many neutrons.
        • Within an unstable nucleus a neutron turns into a proton due to there being too many neutrons.
          • This causes the element that is decaying to change and a beta particle is emitted along with a new stable isotope.
            • The Beta particle is identical to an electron as it has virtually no mass and a -1 charge.
    • Untitled
    • BETA
      • -Small and move quite fast. Penetrates moderately into materials before being stopped.
    • GAMMA
      • After splitting an alpha or beta particle the nucleus may still need to get rid of extra energy. It does this by emitting a gamma ray. This is a type of electromagnetic wave.
        • It has no mass and can penetrate a long way through materials without being stopped.
          • Since gamma rays are just energy it does not change the element of the nucleus that emits it.
    • WHAT TYPE OF RADIATION IS BLOCKED BY WHAT?
      • ALPHA= PAPER AND SKIN
      • BETA=THIN ALLUMINIUM
      • GAMMA= THICK LEAD
    • HALF LIFE
      • The time taken for half of the radioactive nuclei now present to decay.
    • RUTHERFORDS SCATTERING
      • 1909 ERNEST RUTHERFORD, HANS GEIGER AND ERNEST MARSDEN fired alpha particles which were positively charged at thin gold foil. Some went straight though the gold foil and others shot back at them. They soon realised that the nucleus of the gold foil was where the mass was mostly concentrated and was positively charged. The rest was open space. The reason that some of the alpha particles repelled was due to both the positive charges of the alpha and the positive nucleus
    • FORCES WITHIN THE NUCLEUS
      • positively charged protons should repel but they are held together by the strong force.
        • CAN ONLY HOLD PROTONS AND NEUTRONS TOGETHER WHEN SEPERATED BY TINY DISTANCES. IF ANY BIGGER THE FORCE BECOMES WEAK AND IN THEORY DISAPEARS.
    • NUCLEAR FUSION
      • Where two nuclei combine (fuse) together forming a larger nucleus and releasing energy.
        • EXAMPLE= 2 HYROGENS FUSE TO FORM HELIUM AND REALEASED ENERGY.
          • However they can only fuse if they are able to overcome the repulsive electrostatic force and get close enough to be held together by the strong force.
    • E=mcsquared where e=amount of energy released m= amount of mass lost and c= the speed of light through a vacuum.
      • When nuclei undergo fusion of fission they lose mass and release energy.
    • DANGER FROM RADIATION
      • HUMANS= IONISATION CAN DAMAGE THE BODY.
        • HIGH DOSE KILLS CELLS AND THERFORE CAUSES RADIATION SICKNESS.
          • A LOW DOSE CAUSES DAMAGE TO CELLS WHICH CAUSES CANCER
            • EFFECTS; workers in nuclear power plants and miners as many rocks are naturally radioactive.
    • BACKGROUND RADIATION
      • air, soil, rocks etc.
      • space (cosmic rays) which come mostly from the sun
      • Human activity- from nuclear explosions.
    • USES OF IONISING RADIATION
      • TREATING CANCER= High doses of gamma rays can be used to kill all living cells (have to be careful though).
      • Sterilising medical equipment by killing all microbes.
      • Sterilising food in the same way medical equipment is.
    • TRACERS
      • -RADIOACTIV MOLECULES THAT CAN BE INJECTED INTO PEOPLE. THEIR PROGRESS AROUND THE  BODY IS FOLLOWED USING AN EXTERNAL DETECTOR .THEY CAN DETECT CANCER AND WHETHER THE ORGANS IN THE BODY ARE WOKING PROPERLY.
    • NUCLEAR FISSION
      • A nuclear fuel like uranium or plutonium. Neutrons are fired at it causing it to split and form 2 smaller nuclei roughly the same size and lots of energy.

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