Question 1: Define irradiation in the context of radioactivity and explain how it differs from contamination.

Answer: Irradiation is the exposure of objects or people to radiation without contact with radioactive materials, whereas contamination involves radioactive substances physically adhering to or entering an object or person.

Question 2: Describe a real-world example where irradiation is used in environmental science.

Answer: Irradiation is used to sterilise food and medical equipment by exposing them to ionising radiation without making the items radioactive.

Question 1: What is ionising radiation, and why is it important in environmental science?

Answer: Ionising radiation has enough energy to remove electrons from atoms, which can damage living cells and is used in sterilisation, medical treatments, and detecting contamination.

Question 2: Explain how contamination can occur during the use of radioactive materials.

Answer: Contamination occurs when radioactive substances physically adhere to surfaces, or enter the body through ingestion, inhalation, or cuts, leading to internal exposure.

Question 1: A radioactive source emits 5000 particles per second. Calculate the activity in becquerels (Bq).

Answer: Activity (Bq) = number of decays per second = 5000 Bq.

Question 2: A contaminated object has a surface area of 0.05 m² and a contamination level of 200 Bq/m². What is the total contamination on the object?

Answer: Total contamination = contamination level × surface area = 200 Bq/m² × 0.05 m² = 10 Bq.

Question 1: List three safety precautions that must be taken when working with radioactive sources to prevent contamination.

Answer: Use lead shielding, wear protective clothing and gloves, and handle sources with remote tools or robotic devices.

Question 2: Describe a basic procedure to confirm that a radioactive object has not become contaminated during handling.

Answer: Use a Geiger counter or contamination swipe tests to check for radioactive particles on the surface after handling.

Question 1: An environmental scientist measures a level of 150 Bq/m² of radioactive contamination on soil after a nuclear accident. If the area sampled is 0.2 km², what is the total contamination in becquerels? (Note: 1 km² = 1,000,000 m²)

Answer: Surface area in m² = 0.2 km² × 1,000,000 m²/km² = 200,000 m². Total contamination = 150 Bq/m² × 200,000 m² = 30,000,000 Bq.

Question 2: In a certain environmental cleanup, a radioactive waste container is found to have a contamination level of 500 Bq/m² over an area of 0.01 m². Discuss whether this contamination poses a significant health risk and justify your reasoning.

Answer: The contamination level is relatively low, and the total activity is 5 Bq (500 × 0.01). While any radioactive contamination warrants caution, this level suggests limited risk if properly handled. However, precautions should still be taken to prevent internal exposure or spread.

Question 1: Explain how irradiation is used in the sterilisation of medical equipment and how it avoids contamination.

Answer: Irradiation sterilises equipment by exposing it to ionising radiation, killing bacteria and viruses without leaving radioactive residues or causing contamination.

Question 2: Describe a method used to decontaminate areas or objects contaminated with radioactive substances in environmental cleanup efforts.

Answer: Methods include chemical cleaning, removal and disposal of contaminated materials, and using specialised equipment like high-efficiency particulate air (HEPA) filters to capture radioactive particles.