Radioactivity
Overview
Radioactivity is happening all around you right now: faint radiation from rocks, the air, your food and even outer space passes through you every second. Unstable nuclei throw out radiation at random, and learning to identify and measure it is the heart of nuclear physics.
In this lesson you will learn what background radiation is and where it comes from, how radiation is detected and counted, and the nature, ionising effect and penetrating power of alpha, beta and gamma radiation. You will also see how they behave in electric and magnetic fields and how to correct a count rate for background.
Objectives
- Know what is meant by background radiation
- Know the sources that make a significant contribution to background radiation including: (a) radon gas (in the air) (b) rocks and buildings (c) food and drink (d) cosmic rays
- Know that ionising nuclear radiation can be measured using a detector connected to a counter
- Use count rate measured in counts / s or counts / minute
- Describe the emission of radiation from a nucleus as spontaneous and random in direction
- Identify alpha (α), beta (β) and gamma (γ) emissions from the nucleus by recalling: (a) their nature (b) their relative ionising effects (c) their relative penetrating abilities (β+ are not included, β-particles will be taken to refer to β-)
- [Supplement] Use measurements of background radiation to determine a corrected count rate
- [Supplement] Describe the deflection of α-particles, β-particles and γ-radiation in electric fields and magnetic fields
- [Supplement] Explain their relative ionising effects with reference to: (a) kinetic energy (b) electric charge
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Radioactivity. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which is a source of background radiation? A. radon gas B. a torch battery C. a magnet D. sound waves Answer: A
- Alpha radiation is best described as: A. an electron B. a helium nucleus C. an electromagnetic wave D. a proton Answer: B
- Which radiation is stopped by a few millimetres of aluminium? A. alpha B. beta C. gamma D. none of them Answer: B
- Which radiation is NOT deflected by a magnetic field? A. alpha B. beta C. gamma D. all are deflected equally Answer: C
- A counter reads 90 counts/s near a source; background is 10 counts/s. The corrected count rate is: A. 100 counts/s B. 80 counts/s C. 9 counts/s D. 10 counts/s Answer: B
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