Half-life

• What is the half-life of radioactive carbon-14?

  5,730 years
• How much radioactive carbon-14 remains after one half-life if a sample initially contains 64 grams?

  32 grams
• What is the remaining amount of radioactive carbon-14 after two half-lives from an initial 64 grams?

  16 grams
• How can the remaining amount of a radioactive sample be expressed after a given time period?

  • As a fraction
  • As a decimal
  • As a ratio
• If the half-life is two days, how many days would it take for a sample to undergo four half-lives?

  8 days
• If a sample has a count rate of 3,200 Bq at the start, what would be its count rate after 8 days if it decays to 1/16th of its original rate?

  200 Bq
• What is the half-life of cobalt-60 if there are 100 grams in a sample and it is measured after 15 years?

  5 years
• How many half-lives have passed if a sample's activity drops from 1,200 Bq to 300 Bq in 10 days?

  2 half-lives
• What is the definition of half-life in the context of radioactive decay?

  It is the time taken for half of the unstable nuclei in a sample to decay.
• What device detects radiation and gives an electrical signal each time radiation is detected?

  The Geiger-Muller tube
• How is the activity of a radioactive substance measured?

  In Becquerel (Bq)
• What does one Becquerel (Bq) represent?

  One nuclear decay per second
• Describe the process of radioactive decay over time using an example.

  • Activity halves from 80 Bq to 40 Bq in 2 days
  • Activity halves from 40 Bq to 20 Bq in another 2 days
  • Activity halves from 20 Bq to 10 Bq in a third 2-day period
  • Activity never drops to zero but continues to halve
• What happens to a nucleus that has the wrong number of neutrons?

  It can fall apart and regain stability by emitting particles.
• What are the types of radioactive decay and nuclear radiations?

  • Alpha decay
  • Beta decay
  • Gamma radiation
• What is the nature of radioactive decay?

  It is a random process.
• How many trillions of nuclei are typically found in a block of radioactive material?

  Many trillions
• What is the significance of statistical methods in radioactive decay?

  • They help predict when half of the unstable nuclei will decay.
  • They cannot predict when a particular nucleus will decay.