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

Answer: Half-life is the time taken for half of the radioactive nuclei in a sample to decay.

Question 2: Describe the mechanism by which radioactive nuclei decay.

Answer: Radioactive nuclei decay randomly, with each nucleus having a fixed probability of decaying per unit time, resulting in a decrease in the number of undecayed nuclei over time.

Question 3: Explain why the decay of radioactive nuclei is considered a random process but follows a predictable pattern over many nuclei.

Answer: Because each nucleus decays randomly, but statistically, the number of nuclei decaying over a given time interval is consistent, leading to a predictable exponential decay pattern.

Question 1: A sample of a radioactive isotope has an initial activity of 1000 becquerels (Bq). If the activity decreases to 250 Bq in 24 hours, what is the half-life of the isotope? (Use the decay formula: N = N₀ * (1/2)^(t/T))

Answer: The half-life is 12 hours.

Question 2: A certain isotope has a half-life of 8 hours. How much of a 16 gram sample remains after 24 hours? (Show your calculation using the half-life formula.)

Answer: 2 grams remain.

Question 1: Describe a basic experimental setup to measure the half-life of a radioactive isotope. Include safety precautions that must be observed.

Answer: A typical setup involves a Geiger counter or scintillation counter to measure count rates at regular intervals. The sample should be kept in a lead-shielded container to minimise exposure, and all handling should follow safety protocols, including wearing gloves and using tongs. The experiment should be conducted in a well-ventilated area or behind shielding to protect from radiation exposure.

Question 1: A scientist records the activity of a radioactive sample at different times: 0 hours = 800 Bq, 6 hours = 400 Bq, 12 hours = 200 Bq, and 18 hours = 100 Bq. What does this data suggest about the half-life of the isotope?

Answer: The data suggests the half-life is approximately 6 hours, as the activity halves every 6 hours.

Question 2: Based on the data, estimate how much activity would remain after 24 hours if the initial activity is 800 Bq.

Answer: After 24 hours, approximately 50 Bq would remain.

Question 1: Explain how the concept of half-life is important in the real-world application of radioactive dating and medical treatments. Your answer should include at least two points and demonstrate a clear understanding of the concept.

Answer: Half-life allows scientists to determine the age of archaeological samples through radioactive dating by measuring remaining radioactivity. It also helps in medical treatments, such as radiotherapy, where knowing the half-life of isotopes ensures effective dosage and timing to minimise harm to healthy tissue while targeting cancer cells.

Question 1: Identify one industry or field where understanding the half-life of a substance is crucial. Describe its importance in that context.

Answer: In nuclear medicine, understanding the half-life of isotopes like technetium-99m is crucial for timing imaging procedures and ensuring patient safety by using isotopes that decay quickly after their medical use.

Question 2: Explain how knowledge of half-life can influence safety procedures in handling radioactive materials in laboratories.

Answer: Knowing the half-life helps determine how long a radioactive material remains hazardous, guiding safe storage, handling, and disposal procedures to protect workers and the environment.