Half Life/Activity/Decay

• What is Activity?

  'Activity' is the overall rate of decay of all of the radioactive isotopes in our sample.
• Decay is random can take seconds, years or millennia
• what is the first definition of Half life decay?

  the time taken for No of radioactive nuclei in a sample to HALVE
• Second definition of half life decay

  Time taken for the No of decays/activity to halve
• what is a Geiger counter

  a machine that records all decay per second, by count rates
• what is activity measure in?

  Becquerels- Bq 1Bq=1 decay per second
• Equation for count rate

  Count rate= Initial count/2h
• There isn't an equation for half-lives but work this out- The half-life of a source is 40 Hrs, and the source has 3 Million radioactive Nuclei, How many nuclei remain after Five days?

  24x5=120Hrs

  120Hrs/40Hrs=3 Half-lives(in 120Hrs)

  (1/2)to the power of 3 x 3Million =(.5x.5.x.5)x 3000000

  3000000*.5*.5*.5=37500

  375000 Nuclei after 5 days!
• Half lives sequence - work out how many half lives there are (time/ time for life to halve) then nuclear / 2^n number of halve lives
• What is nuclear fission?

  Nuclear fission is a process in which the nucleus of an atom is split into two or more smaller nuclei

  releasing a significant amount of energy

  more neutrons are released, creating a chain reaction.
• What is nuclear fusion?

  The process of combining two atomic nuclei to form a heavier nucleus, releasing a large amount of energy in the process.

  although binding energy is endothermic, it depends on the nuclei, so it releases energy