What are alpha, beta and gamma radiation, and what are their uses and hazards?
The structure of the atom, alpha, beta and gamma radiation, their penetrating power and ionising effect, background radiation, and the uses and hazards of radiation.
A focused answer to WJEC GCSE Physics topic 2.7 on types of radiation, covering the structure of the atom, alpha, beta and gamma radiation, their penetrating power and ionising ability, background radiation, and the uses and hazards of ionising radiation.
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What this topic is asking
WJEC wants you to describe the atom, identify the three types of nuclear radiation and their properties, explain background radiation, and discuss the uses and hazards of radiation. This is topic 2.7 Types of radiation in Unit 2 of WJEC GCSE Physics (3420).
The atom and radiation
Alpha, beta and gamma radiation
The three types behave differently in magnetic and electric fields because of their charge: alpha (positive) and beta (negative) are deflected in opposite directions, while gamma (no charge) passes straight through. The more strongly a radiation ionises, the more quickly it loses its energy to the matter it travels through, which is exactly why the most strongly ionising radiation (alpha) is also the least penetrating: it deposits all its energy over a very short distance.
Ionisation means knocking electrons off atoms to leave charged ions. This is what makes radiation both useful and hazardous: in a smoke detector the ionisation of the air by an alpha source carries a tiny current that smoke interrupts, but the same ionising effect inside living tissue can damage cells.
Background radiation, uses and hazards
Try this
Q1. State what absorber stops beta radiation. [1 mark]
- Cue. A few millimetres of aluminium.
Q2. Name one natural source of background radiation. [1 mark]
- Cue. Radon gas, rocks and soil, or cosmic rays (any one).
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20183 marksDescribe the penetrating power of alpha, beta and gamma radiation.Show worked answer →
A topic 2.7 Describe question. Alpha is the least penetrating and is stopped by a sheet of paper or a few centimetres of air (1 mark). Beta is more penetrating and is stopped by a few millimetres of aluminium (1 mark). Gamma is the most penetrating and is only reduced by thick lead or concrete (1 mark). Markers reward the correct absorber for each type. A common error is to swap alpha and gamma.
WJEC 20214 marksExplain why alpha radiation is the most dangerous if a source is swallowed, but the least dangerous outside the body.Show worked answer →
A topic 2.7 Explain question. Alpha is strongly ionising because it is large and highly charged (1 mark). Outside the body it cannot penetrate the skin, so it does little harm (1 mark). Inside the body there is no skin to stop it, so it deposits all its energy in nearby cells (1 mark) and its strong ionisation causes the most damage to tissue (1 mark). Markers reward strong ionisation, being stopped by skin outside, and the damage inside. A common error is to say alpha is harmless because it is weakly penetrating.
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Sources & how we know this
- WJEC GCSE Physics specification (3420) from 2016 — WJEC (2016)