last minute

• alpha

  He nucleus

  +2 relative charge

  4u = mass
• beta-minus

  very fast electron

  -1 relative charge
• beta-plus

  positron

  +1 relative chage
• gamma

  high frequency EM wave

  o relative charge

  0 mass
• alpha

  slow speed

  strong ionising power (10^4 ions per mm in air at standard pressure)

  absorbed by paper or a few cm of air

  range is up to 100nm

  deflected in a magnetic field
• beta-minus

  fast speed

  weak ionising power (100 ions per mm in air at standard pressure)

  absorbed by approx 3mm of aluminium

  range in air approx 1m

  deflected in a magnetic field opposite to an alpha particle and more easily
• Beta plus

  annihilated by electro, so virtually zero range
• gamma

  speed of light

  very weak ionising power

  absorbed by several cm of lead/concrete

  following an inverse-square law in air

  isn't deflected in a mag field
• the radiation source and detector can be used to monitor the thickness of aluminium foil, paper and steel during manufacturing

  the materials are flattened as they are fed through rollers. the radiation source and detector are placed on either side of the material

  the thicker the material the greater the amount of radiation absorbed hence, the count rate recorded changed with thickness. as a consequence, the position of the roller is adjusted in order to produce a thinner material or restore it to the original thickness
• gamma radiation

  radioactive tracers - short half-life, can be injected into a patient. the gamma radiation can be detected using gamma cameras in order to help diagnose patients

  sterillisation of surgical equipment - kills any bacteria present on the equipment

  radiation therapy - gamma radiaiton can be used to kill cancerous cells in a targeted region of the body (tumour). however it will also kill any healthy cells in that region to
• radioactive isotope carbon-14 is used for radioactive dating

  CO2 is taken in by plants at a constant rate while they are alive, during the process of photosunthesis, when they die, however, the activity of the carbon-14 begin to fall. sample of once-living materials can be tested to determine the current amount of carbon-14 present, and hence dated by comparing to the expected original amount
• it can be difficult to be accurate with radioactive dating

  the dample size or count rage may be small and hence statistically unreliable

  the activity may be too small and indistinguishable from the background activity

  the sample may have been contaminated by other radioactive soucres

  for human-made objects, you can only find the age of the material used to make the object, not the age of the object itself

  there may be uncertainty in the amount of carbon-14 that existed many years ago
• Techntium-99m is widely used in medical tracers - radioactive substances that are used to show tissue or organ function

  the tracer is injected into or swallowed by the patient. it then moves through their body to the region on interest. an external detector is used to record the radiation emitted, allowing an internal image of the patient to be produced
• Technetium-99m is suitable as has a half-life of 6 hours

  sufficient time for data to be obtained and short enough to limit the radiation to an acceptable level