Radioactive Decay and Half Life

Cards (27)

  • What are the two terms discussed in the video?
    Activity and half-life
  • What happens to unstable isotopes to become more stable?
    They decay by emitting radiation
  • What do we call materials that emit radiation?
    Radioactive materials
  • Why can't we predict when a single radioactive isotope will decay?
    The decay process is completely random
  • What can we determine from a large sample of radioactive isotopes?
    The activity and half-life of the sample
  • How is activity measured?
    In becquerels
  • What does one becquerel represent?
    One decay per second
  • If a sample has an activity of 600 becquerels, how many isotopes decay each second?

    600 isotopes decay each second
  • What is half-life defined as?
    The time taken for the number to halve
  • How can half-life be defined in terms of radioactive nuclei?
    Time taken for nuclei to halve
  • How can half-life be defined in terms of activity?
    Time taken for activity to halve
  • What happens to the number of unstable particles as time goes on?
    The number of unstable particles decreases
  • Why does the overall rate of decay decrease over time?
    Fewer particles are left to decay
  • How is the decay process represented graphically?
    Activity plotted against time
  • What does the curve of the decay graph indicate?
    The rate of decline also falls
  • How do you calculate half-life from a graph?
    Find the time for activity to halve
  • If the activity drops from 600 to 300, how long did it take?
    About two hours
  • If the activity drops from 300 to 150, how long does it take?
    Another two hours
  • What does a shorter half-life indicate about a radioactive sample?
    It decays more quickly
  • What device is used to find the activity of a radioactive sample?
    Geiger Muller tube
  • What does a Geiger Muller tube record?
    Decays that reach it each second
  • What is the count rate used for?
    To estimate the activity
  • If the half-life of a radioactive source is 40 hours, how many half-lives are in five days?
    Three half-lives
  • How many radioactive nuclei remain after three half-lives from 3 million?
    375,000 nuclei remain
  • What are the key concepts of activity and half-life in radioactive decay?
    • Activity: overall rate of decay
    • Measured in becquerels
    • Half-life: time for quantity to halve
    • Correlated with number of radioactive nuclei
  • How does the decay process of radioactive isotopes change over time?
    • Decay is random for individual isotopes
    • Overall decay rate decreases as particles decay
    • Activity declines and is represented by a curved graph
  • How do you calculate the remaining radioactive nuclei after multiple half-lives?
    1. Determine total time in hours
    2. Divide by half-life to find half-lives
    3. Halve the initial quantity for each half-life