Question 1: Define the term 'half-life' in the context of radioactive decay.

Answer: The time taken for the activity of a radioactive source to decrease to half of its original value.

Question 2: Explain why the half-life of a radioactive isotope is considered a constant for a given isotope.

Answer: Because the probability of decay of each nucleus remains constant over time, making the half-life independent of the amount or activity.

Question 1: A sample of a radioactive isotope has an activity of 80 Bq. Its half-life is 3 hours. What will be its activity after 9 hours? (Use the decay formula: N = N₀ × (1/2)^{t / T_{1/2}}).

Answer: 10 Bq

Question 2: A researcher measures a sample's activity as 200 Bq. After 6 hours, the activity drops to 25 Bq. Calculate the half-life of the isotope.

Answer: 3 hours

Question 1: Outline the key steps and safety precautions involved in measuring the half-life of a radioactive source.

Answer: To investigate half-life, a sample should be safely contained in a lead-shielded environment, with a detector positioned at a fixed distance. The activity should be measured at regular intervals over a period covering multiple half-lives. Safety precautions include wearing protective clothing, handling the source with tongs or remote tools, and ensuring proper waste disposal. Data collected can be analysed to determine the half-life by plotting activity against time or using decay equations.

Question 1: A radioactive sample has an initial activity of 160 Bq. After 4 hours, the activity is measured at 20 Bq. Using this data, estimate the half-life of the isotope.

Answer: 2 hours

Question 1: Describe how the concept of half-life is used in radiocarbon dating to estimate the age of archaeological samples.

Answer: Radiocarbon dating relies on measuring the remaining amount of carbon-14 in a sample. Since carbon-14 has a known half-life of about 5730 years, the proportion of remaining carbon-14 indicates how many half-lives have elapsed, allowing scientists to estimate the time since the organism's death.

Question 2: Multiple Choice: Which of the following best describes why half-life is an important concept in nuclear medicine?

Answer: It helps in scheduling the timing of radioactive treatments to minimise exposure.

Question 1: Discuss how half-life information is used in the management of nuclear waste.

Answer: Half-life data helps determine how long radioactive waste remains hazardous, guiding storage duration and safety protocols to protect people and the environment.