Question 1: Define alpha radiation and describe its properties.

Answer: Alpha radiation consists of helium nuclei (2 protons and 2 neutrons). It has a positive charge, is stopped by a sheet of paper or skin, and has low penetration power.

Question 2: Explain how beta particles are produced in radioactive decay.

Answer: Beta particles are high-energy electrons or positrons emitted when a neutron in an unstable nucleus transforms into a proton (or vice versa), during beta decay.

Question 3: List two characteristics of gamma radiation.

Answer: Gamma radiation is electromagnetic radiation with very high frequency, has no mass or charge, and can penetrate many materials. It is emitted alongside alpha or beta particles in decay.

Question 1: A sample of radioactive material emits 500 alpha particles per second. Calculate the activity in becquerels (Bq).

Answer: Activity = number of decays per second = 500 Bq.

Question 2: If a radioactive isotope has a half-life of 10 hours, how much of a 100 g sample remains after 30 hours? (Assume no other processes occur.)

Answer: Remaining mass = initial mass × (1/2)^(time/half-life) = 100 × (1/2)^(30/10) = 100 × (1/2)^3 = 100 × 1/8 = 12.5 g.

Question 1: Describe a safety procedure that must be followed when handling gamma radiation sources in a laboratory.

Answer: Use lead shielding to block gamma rays, wear appropriate protective clothing, and minimise exposure time. Maintain a safe distance from the source.

Question 2: Identify the variables involved in designing an experiment to measure the penetration of beta particles through different materials.

Answer: Variables include the type and thickness of the material used, energy of the beta source, distance between source and detector, and the type of detector. Controlled variables should include source strength and measurement conditions.

Question 1: A sample of beta radiation has an initial count rate of 200 counts per second. After passing through 2 mm of aluminium, the count rate drops to 50 counts per second. Explain what this data suggests about beta particle penetration.

Answer: The data indicates that aluminium absorbs or scatters some beta particles, reducing the number that reach the detector. The material's thickness affects the penetration; more thickness would further reduce the count rate.

Question 1: Describe an application of gamma radiation in medical diagnosis.

Answer: Gamma rays are used in medical imaging techniques such as PET scans, where they help to create images of the inside of the body after a radioactive tracer is administered.

Question 2: Explain why alpha emitters are used in smoke detectors.

Answer: Alpha emitters ionise the air inside a chamber, allowing a small current to flow. When smoke enters, it neutralises the ions, stopping the current and triggering the alarm.