What are the types of nuclear radiation, and how do their properties differ?
Nuclear radiation: the nature and properties of alpha, beta and gamma radiation, their ionising ability and penetrating power, what ionisation means, and the activity of a source.
An SQA National 5 Physics answer on nuclear radiation, covering the nature of alpha, beta and gamma radiation, their ionising ability and penetrating power, what ionisation means and why it is harmful, the activity of a source measured in becquerels, and the uses of each type of radiation.
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What this key area is asking
The SQA wants you to describe the three types of nuclear radiation, compare their ionising ability and penetrating power, explain what ionisation is and why it is harmful, and calculate the activity of a source.
The three types of radiation
Alpha and beta are particles with mass and charge; gamma is a wave with no mass or charge. This difference explains why they behave so differently when they travel through materials.
Ionising ability and penetrating power
This is a frequent SQA question, so learn the pairing: alpha is a strong ioniser that is easily stopped, while gamma is a weak ioniser that travels a long way. The two properties are linked, because a strong ioniser deposits its energy quickly and so does not get far.
What ionisation is and why it matters
Because alpha is strongly ionising, it is very dangerous if a source gets inside the body (for example by being breathed in or swallowed), even though outside the body it is stopped by skin. Gamma, being penetrating, is the main hazard from a source outside the body.
Activity of a source
Uses of nuclear radiation
Each type has uses that match its properties. Alpha is used in some smoke detectors (its short range makes it safe in a sealed detector). Beta is used in thickness monitoring of paper or foil, because the amount getting through depends on the thickness. Gamma is used to sterilise medical equipment, to treat cancer, and as a medical tracer, because it penetrates the body and can be detected outside.
Try this
Q1. Name the three types of nuclear radiation. [1 mark]
- Cue. Alpha, beta and gamma.
Q2. State what material is needed to stop beta radiation. [1 mark]
- Cue. A few millimetres of aluminium.
Q3. A source produces decays in . Calculate the activity. [2 marks]
- Cue. .
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style3 marksState the three types of nuclear radiation, and put them in order of increasing penetrating power.Show worked answer →
The three types of nuclear radiation are alpha, beta and gamma.
In order of increasing penetrating power: alpha (least penetrating, stopped by paper or skin), then beta (stopped by a few millimetres of aluminium), then gamma (most penetrating, reduced only by thick lead or concrete).
Markers reward naming all three types and the correct order of penetrating power, with alpha the least and gamma the most penetrating.
SQA N5 style4 marksA radioactive source produces 4800 decays in 2 minutes. Calculate the activity of the source in becquerels.Show worked answer →
Activity is the number of decays per second, so first convert the time to seconds: .
Relationship: .
Substitution: .
Markers reward converting the time to seconds, selecting the activity relationship, and a final answer in becquerels (), where one becquerel is one decay per second.
Related dot points
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An SQA National 5 Physics answer on half-life, covering what half-life means, how the activity and number of undecayed nuclei halve each half-life, how to find a half-life from a table or a decay graph, how to work out the activity after a number of half-lives, and uses such as carbon dating and medical tracers.
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Sources & how we know this
- SQA National 5 Physics Course Specification — SQA (2019)