radiation properties

• • range of radiation depends on its type and the material its travelling through
  • alpha particles dont get very far before they start hitting atoms - they are the least penetrating
  • beta particles can travel quite far before hitting an atom
  • gamma radiation travels a long way before hitting an atom - it is the mot penetrating
• • alpha particles are blocked by paper/dead skin
  • beta particles are blocked by a few cm of aluminium
  • gamma rays are blocked by thick lead/a few m of concrete
• • when balancing nuclear equations pay attention to the radiation type at the end and ensure that the number of protons and neutrons are equal
• • half life is the time it takes for the radioactive activity of a source to half
  • half life is a totally random process so there are often variations
  • activity = initial activity /2n (n is number of half lives)
  • use the dice practical to simulate dice
• • ionising radiation harms cells
  • radioactive processes have waste products
• • high doses of radiation can be used to kill livng cells and so can be used to treat cancers
  • specific doses must be used depending on the size and type of the tumour
  • however a fair bit od damage occurs to the living cells so the patent must be aware that the benifits outweigh the risk
• • to treat cancer on the outside of the body gamma rays are focused on the tumour uising a wide beam
  • the patient remains still and the beam i roatated around the to ensure the tumour remains at the center and minimises exposure to healthy cells
• • to treat cancer internally implants containing beta-emitters placed next to or inside the tumour and have a short range to so they dont damage the healthy cells
  • an implant with a long half life and so should be removed and if its half life is short the implant is left
  • alpha emitters are injected into tumour, strongly ionising so they do lots of damage to the cancer cells
• • background radiation is the low level radiation that is present all the time wherever you go, it can be natural or artificial
  • everyone gets a small does from background radiation
  • dont ignore when doing experiments, measure the mean background radiation over a long enough perod of time and subtract from the count rate you measure
• nuclear fission

  • spliting one large nuclei into two small nuclei
  • huge amount of energy released in chain reactions
• • chain reactions are carefully controlled in reactors
  • fuel rods - uranium and absorb the nuclei when they collide
  • moderator - usually water or graphite slow down the fast moving neutrons
  • control rods - used to absorb more neutrons and control the rate of fission
  • produces a varaity of waste with different half lives
• • alpha particles are two neutrons
  • beta is high energy electrons
  • gamma is electromagnetic waves
• • nucleon number on top
  • proton number on bottom