Exam Focus — Radiation Detection

🎯 Exam Focus — Radiation Detection

Examined in Edexcel 1PH0/1 (Paper 1). Edexcel CP9 (Radioactive Decay Core Practical) directly assesses radiation detection — students are expected to explain how a GM tube works (ionisation of gas, ion movement, current pulse) and describe its use in measuring count rate over time. Film badge questions asking students to explain what the badge monitors (not what it blocks) are a reliable 2-mark item on Edexcel 1PH0/1.

Most Common Question Types

• Explain how a GM tube detects radiation [3-4 marks] — must mention ionisation of gas, ion movement, and current pulse
• Describe what cloud chamber tracks look like for alpha and beta [3 marks]
• Explain why radiation workers wear film badges [2 marks]
• Calculate corrected count rate from measured count and background [2 marks]
• Compare two detectors for a specific application [3 marks]

What Examiners Want to See

For GM tube questions, the key physics is: radiation ionises the gas (not "detects" — be specific), the ions are accelerated by the electric field, their movement constitutes a current pulse, and each pulse is counted. Many students write "it detects radiation" without explaining the ionisation mechanism — this scores few marks.