Radioactive decay & Half life

• What are the two terms discussed in the video related to radioactive materials?

  Activity and half-life
• What happens to unstable isotopes to become more stable?

  They decay by emitting radiation
• How can we predict the decay of a large sample of radioactive isotopes?

  We can find out the activity and half-life of the sample
• How is activity measured?

  In becquerels
• What does one becquerel represent?

  One decay per second
• What is the definition of half-life?

  The time taken for the number of radioactive nuclei or activity to halve
• If a sample has an initial activity of 600 decays per second, what would its activity be after one half-life?

  300 decays per second
• How does the decay process of radioactive isotopes appear over time?

  The overall rate of decay decreases as fewer particles remain
• What is the relationship between the number of radioactive nuclei and activity over time?

  • Fewer radioactive nuclei lead to lower activity
  • Activity decreases as the number of unstable particles decreases
  • Both are correlated and define the decay process
• What does a graph plotting activity against time show about radioactive decay?

  The activity declines over time and the rate of decline also falls
• How can you calculate the half-life from a graph of activity over time?

  By finding the time it takes for the activity to halve
• What is the half-life of the sample in the example given in the video?

  Two hours
• What device is used to measure the activity of a radioactive sample in real life?

  A Geiger-Muller tube
• What does a Geiger-Muller tube record?

  All the decays that reach it each second
• If the half-life of a radioactive source is 40 hours, how many half-lives are there in five days?

  Three half-lives
• How many radioactive nuclei remain after three half-lives if you start with 3 million nuclei?

  375,000 nuclei
• What are the steps to calculate the remaining radioactive nuclei after a certain number of half-lives?

  1. Determine the total time and convert to hours
  2. Divide by the half-life to find the number of half-lives
  3. Start with the initial number of nuclei
  4. Halve the number of nuclei for each half-life