What is radioactivity and how is it related to nuclear physics?

Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation. It is a key concept in nuclear physics, which studies the components and behavior of atomic nuclei. Understanding radioactivity is essential for Cambridge IGCSE Physics students as it explains how elements transform and the types of radiation emitted.

What are the different types of radioactive decay?

The three main types of radioactive decay are alpha decay, beta decay, and gamma decay. Alpha decay involves the emission of an alpha particle, which consists of 2 protons and 2 neutrons. Beta decay occurs when a neutron in the nucleus transforms into a proton, emitting a beta particle (an electron or positron). Gamma decay involves the release of gamma rays, which are high-energy photons, and usually follows alpha or beta decay to release excess energy.

How can we measure radioactivity?

Radioactivity is measured using instruments like Geiger-Müller counters, scintillation counters, and cloud chambers. These devices detect and count the particles emitted by radioactive substances. The activity of a radioactive source is measured in becquerels (Bq), which indicates the number of decays per second. Understanding these measurements is crucial for Cambridge IGCSE students to grasp the practical aspects of nuclear physics.

What are the safety precautions when handling radioactive materials?

When handling radioactive materials, it is important to minimize exposure by using shielding, maintaining a safe distance, and limiting time spent near sources. Protective clothing and proper storage are also essential. These precautions help prevent harmful effects of radiation, such as tissue damage and increased cancer risk. Cambridge IGCSE Physics curriculum emphasizes the importance of safety in experiments involving radioactivity.

How does radioactivity impact the environment and human health?

Radioactivity can have significant impacts on the environment and human health. Exposure to high levels of radiation can cause acute health effects, such as radiation sickness, and increase the risk of cancer. Environmental contamination can occur through nuclear accidents or improper disposal of radioactive waste, affecting ecosystems and human populations. Understanding these impacts is part of the Cambridge IGCSE Physics syllabus, highlighting the importance of responsible use and management of radioactive materials.

Why is "Reading half-life from one specific point on the graph" a common mistake in Radioactivity?

Why it happens: Treating the curve as linear. How to avoid it: Half-life is constant: take an average from MULTIPLE drops (e.g. 1000 500, 500 250). Source: 0625/42 — recurring

Why is "Failing to balance $A$ AND $Z$" a common mistake in Radioactivity?

Why it happens: Only checking the mass number. How to avoid it: BOTH A and Z must balance on every nuclear equation.

Why is "Saying $\alpha$ is an EM wave" a common mistake in Radioactivity?

Why it happens: Confusing with . How to avoid it: = helium NUCLEUS (matter). Only is EM.

Why is "Saying decay is caused by temperature or pressure" a common mistake in Radioactivity?

Why it happens: Comparing to chemical reactions. How to avoid it: Radioactive decay is SPONTANEOUS and RANDOM — independent of physical conditions.

Nuclear PhysicsCambridge IGCSE Physics (0625)

Radioactivity

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Radioactivity — Cambridge IGCSE 0625 Physics Extended (2026)

Alpha, beta, gamma — what they are, what they do, and how they decay. Plus half-life, background radiation, and uses and dangers.

What you’ll learn

Mapped to the Cambridge IGCSE 0625 syllabus (2026-2028).

5.2 — Describe properties of alpha, beta and gamma radiation.
5.2 — Write nuclear equations for alpha and beta decay.
5.2 — Define half-life and use decay graphs.
5.2 — Describe sources of background radiation and uses/dangers of radioactivity.

Alpha, beta, gamma — properties

$\alpha$ : heavy helium nucleus. $\beta$ : fast electron. $\gamma$ : EM wave.

Property	Alpha ( $\alpha$ )	Beta ( $\beta^{-}$ )	Gamma ( $\gamma$ )
Identity	Helium-4 nucleus, $^{4}_{2}\text{He}$	High-energy electron, $^{0}_{-1}\text{e}$	EM wave (photon)
Charge	$+2$	$-1$	$0$
Mass	$\approx 4\,\text{u}$	$\approx 1/1836\,\text{u}$	$0$
Speed	$\sim 5\%$ of light	Up to $\sim 99\%$ of light	Speed of light
Ionising power	HIGH	Medium	LOW
Penetrating power	Low	Medium	High
Stopped by	Paper, skin, $\sim 5\,\text{cm}$ air	Few mm aluminium	Thick lead / concrete
Deflected by E or B field?	Yes (slightly, $+ve$ )	Yes (more, $-ve$ )	No

Inverse relationship. More ionising → less penetrating (alpha rips through atoms quickly so loses energy fast).

In a magnetic field: alpha and beta deflect in OPPOSITE directions because they have opposite charges. Gamma doesn't deflect at all.

Alpha: He nucleus, $+2$ , paper-stopped.
Beta: electron, $-1$ , mm-Al-stopped.
Gamma: EM wave, no charge, lead-stopped.
More ionising = less penetrating.

Decay equations

Balance proton number ( $Z$ ) and nucleon number ( $A$ ) on both sides.

Alpha decay. $^{A}_{Z}\text{X} \to ^{A-4}_{Z-2}\text{Y} + ^{4}_{2}\alpha.$

The nucleus loses 2 protons and 2 neutrons (a helium nucleus).

Worked. Uranium-238 alpha-decays to thorium-234. $^{238}_{92}\text{U} \to ^{234}_{90}\text{Th} + ^{4}_{2}\alpha.$ $Z$ : $92 = 90 + 2$ ✓. $A$ : $238 = 234 + 4$ ✓.

Beta decay. $^{A}_{Z}\text{X} \to ^{A}_{Z+1}\text{Y} + ^{0}_{-1}\beta.$

A neutron in the nucleus turns into a proton, ejecting an electron (the beta particle). $Z$ goes UP by 1; $A$ stays the same.

Worked. Carbon-14 beta-decays to nitrogen-14. $^{14}_{6}\text{C} \to ^{14}_{7}\text{N} + ^{0}_{-1}\beta.$

Gamma decay. An excited nucleus emits a gamma photon, releasing energy. NEITHER $A$ nor $Z$ change.

Cambridge tip. Always check both $A$ and $Z$ balance; that's the check that you've done it right.

Alpha: $A$ down 4, $Z$ down 2.
Beta: $Z$ up 1, $A$ unchanged.
Gamma: no change in $A$ or $Z$ .
Balance both sides — check both numbers.

Half-life

Time for half the nuclei to decay. Each half-life HALVES the count.

Half-life $t_{1/2}$ is the time for HALF the radioactive nuclei in a sample to decay (or for the activity to halve).

Each successive half-life halves the count again.

After 1 half-life: $1/2$ remains.
After 2: $1/4$ .
After 3: $1/8$ .
After $n$ : $(1/2)^{n}$ .

Half-life is a random-process AVERAGE. The decay is random per nucleus; we can't say WHICH nucleus decays next, but the bulk obeys the half-life law.

Worked. A sample's activity is $800\,\text{Bq}$ now. Half-life is $5\,\text{years}$ . Activity in $20\,\text{years}$ ?

$20/5 = 4$ half-lives.
$800 \times (1/2)^{4} = 800/16 = 50\,\text{Bq}$ .

Half-life from a graph. Plot activity (or count rate) vs time. Read off the time for activity to halve. Check by reading another half (e.g. quarter to eighth) — should give the same time.

Common half-lives.

Iodine-131: 8 days.
Carbon-14: 5730 years.
Uranium-238: 4.5 billion years.

Half-life: time to halve.
After $n$ half-lives, fraction left = $(1/2)^{n}$ .
Different isotopes: vastly different $t_{1/2}$ .
Activity decay graph: exponential.

Uses, dangers, and background radiation

Radiation is everywhere — cosmic, terrestrial, medical. Uses include tracing, sterilising, dating. Dangers: cell damage, mutation, cancer.

Sources of background radiation.

Cosmic rays from space.
Radon gas from rocks (especially granite).
Food and drink (e.g. potassium-40).
Medical (X-rays, radiotherapy).
Nuclear power & weapons fallout (small).

When measuring an experimental sample's activity, ALWAYS subtract background activity from the measured value.

Uses.

Smoke detectors (alpha source, americium-241): smoke disrupts an ionised current → alarm.
Cancer treatment (gamma): targeted gamma kills tumour cells.
Sterilising medical equipment with gamma.
Tracers in medicine (small, short half-life iodine for thyroid imaging).
Carbon dating (carbon-14 half-life of 5730 years).
Industrial thickness measurement with beta sources (changing thickness changes count rate).
Smoke detectors and alarms.

Dangers.

Ionising radiation damages DNA → mutation, cancer.
Acute high doses cause radiation sickness, organ failure, death.
Long-term low-dose exposure can be cumulative.

Safety precautions.

Distance: more distance = lower intensity (inverse-square).
Shielding: lead aprons, concrete walls, soil cover.
Time: limit exposure duration.
Containment: store sources in lead-lined boxes, use tongs.

Choosing the right radiation for the job.

Alpha: only useful inside the body (medical) where its high ionising power kills targeted cells. Don't use alpha for diagnostic imaging since it doesn't escape the body.
Beta: thickness gauges, medical tracers (β source needs to leave the body for detection).
Gamma: most penetrating, best for sterilising and cancer treatment outside the body.

Background: cosmic, radon, food, medical.
Subtract background in experiments.
Uses: medical, dating, industrial.
Safety: distance, shielding, time, containment.

How it’s examined

Radioactivity appears every Paper 4 (8-10 marks) — typically a properties table, a balanced decay equation, then a half-life graph or calculation. Examiner reports flag wrong $Z$ -change in beta decay (students drop it instead of raise) and missing the random nature of decay (Cambridge wants 'random' explicitly).

Sources: Cambridge IGCSE Physics 0625 syllabus 2026-2028 (5.2); 0625/42 Oct/Nov 2024 — Q19 (half-life, decay equation); 0625 Examiner Reports 2022-2024. Last reviewed 2026-05-06.

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Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

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Step-by-step worked examples — Radioactivity

Step-by-step solutions to past-paper-style questions on radioactivity, written exactly the way a tutor would explain them at the board.

1Compare $\alpha$ , $\beta$ and $\gamma$
Core• properties
Question
State the nature, charge and stopping material for each of $\alpha$ , $\beta$ and $\gamma$ radiation.
Step-by-step solution
1. Step 1
  $\alpha$ : helium nucleus, $+2$ , stopped by paper.
2. Step 2
  $\beta$ : high-energy electron, $-1$ , stopped by a few mm of aluminium.
3. Step 3
  $\gamma$ : EM wave, $0$ , reduced (not fully stopped) by lead.
Answer
See descriptions above.
2Balance an $\alpha$ decay
Extended• Adapted from 0625/42 May/Jun 2024 Q19• nuclear equation
Question
$^{226}_{88}\text{Ra}$ undergoes $\alpha$ decay. Write the equation.
Step-by-step solution
1. Step 1
  $\alpha$ particle = $^{4}_{2}\text{He}$ .
2. Step 2
  Subtract from parent: $A = 226 - 4 = 222$ , $Z = 88 - 2 = 86$ .
3. Step 3
  $Z = 86$ is radon (Rn).
  $^{226}_{88}\text{Ra} \rightarrow {}^{222}_{86}\text{Rn} + {}^{4}_{2}\text{He}$
Answer
$^{226}_{88}\text{Ra} \to {}^{222}_{86}\text{Rn} + {}^{4}_{2}\text{He}$
3Balance a $\beta^{-}$ decay
Extended• beta
Question
$^{14}_{6}\text{C}$ undergoes $\beta^{-}$ decay. Write the equation.
Step-by-step solution
1. Step 1
  $\beta^{-}$ particle = $^{0}_{-1}\text{e}$ . A neutron becomes a proton.
2. Step 2
  $A$ unchanged ( $14$ ); $Z$ increases by $1$ ( $\to 7$ = N).
  $^{14}_{6}\text{C} \rightarrow {}^{14}_{7}\text{N} + {}^{0}_{-1}\text{e}$
Answer
$^{14}_{6}\text{C} \to {}^{14}_{7}\text{N} + {}^{0}_{-1}\text{e}$
4Half-life calculation
Extended• half-life
Question
An isotope has half-life $5\,\text{days}$ . Starting activity is $800\,\text{Bq}$ . Find activity after $20\,\text{days}$ .
Step-by-step solution
1. Step 1
  Number of half-lives.
  $n = 20/5 = 4$
2. Step 2
  Halve $4$ times.
  $A = 800 \times \left(\dfrac{1}{2}\right)^{4} = 50\,\text{Bq}$
Answer
$50\,\text{Bq}$
5Identify a radiation from penetration
Core• identification, penetration
Question
A radiation passes through paper and a few millimetres of aluminium, but is significantly reduced by a thick block of lead. Name the radiation and state its charge.
Step-by-step solution
1. Step 1
  Stopped by paper → $\alpha$ . Stopped by a few mm aluminium → $\beta$ . Only reduced by lead → $\gamma$ .
2. Step 2
  The radiation here passes paper AND aluminium but is attenuated by lead → it must be $\gamma$ .
Answer
$\gamma$ radiation. Charge $= 0$ .
6Match radiation to application
Core• application
Question
Identify the appropriate radiation for each application: (a) thickness monitoring of aluminium foil during manufacture, (b) sterilising single-use medical instruments, (c) a medical tracer that must travel through the body.
Step-by-step solution
1. Step 1
  (a) Foil monitor: needs radiation that PASSES through thin foil but is sensitive to its thickness — $\beta$ (alpha is stopped by foil; gamma is too penetrating to be sensitive).
2. Step 2
  (b) Sterilisation through packaging: needs deep penetration to reach all parts → $\gamma$ .
3. Step 3
  (c) Medical tracer: must travel through tissue and be detected outside the body → $\gamma$ (alpha and beta are absorbed by tissue and cause more damage internally).
Answer
(a) $\beta$ . (b) $\gamma$ . (c) $\gamma$ .
7Background-radiation correction
Extended• Adapted from 0625/42 May/Jun 2023 Q11• background, count rate
Question
A GM tube records $32\,\text{counts/s}$ near a sample. With the sample removed, the background rate is $8\,\text{counts/s}$ . The half-life of the sample is to be measured. After $1\,\text{half-life}$ , what GM-tube reading should the student expect?
Step-by-step solution
1. Step 1
  True initial activity of the sample = total $-$ background.
  $A_{0} = 32 - 8 = 24\,\text{counts/s}$
2. Step 2
  After 1 half-life the SAMPLE'S activity halves.
  $A_{1} = 24/2 = 12\,\text{counts/s}$
3. Step 3
  Background continues at $8\,\text{counts/s}$ , so the GM-tube reads $A_{1} + 8$ .
  $\text{reading} = 12 + 8 = 20\,\text{counts/s}$
Answer
GM-tube reading $= 20\,\text{counts/s}$ .
Examiner tip
The examiner report flags candidates often halving the RAW reading $32 \to 16$ . Half-life applies to the SAMPLE'S activity only, after subtracting background — and the background must be ADDED BACK to the final reading.
8Read half-life off a decay graph
Extended• graph, half-life
Question
An activity-time graph starts at $400\,\text{Bq}$ . The activity falls to $200\,\text{Bq}$ at $t = 6\,\text{minutes}$ , to $100\,\text{Bq}$ at $t = 12\,\text{minutes}$ , and to $50\,\text{Bq}$ at $t = 18\,\text{minutes}$ . State the half-life and explain how you can be confident.
Step-by-step solution
1. Step 1
  Each halving takes the same interval — characteristic of an exponential decay.
2. Step 2
  $400 \to 200$ : $6\,\text{min}$ . $200 \to 100$ : $12 - 6 = 6\,\text{min}$ . $100 \to 50$ : $18 - 12 = 6\,\text{min}$ .
3. Step 3
  Average from three half-lives = $6\,\text{min}$ — consistent → half-life $= 6\,\text{min}$ .
Answer
Half-life $= 6\,\text{minutes}$ (confirmed by three consecutive halvings each taking $6$ minutes).
9How many half-lives have passed?
Extended• half-life, ratio
Question
The activity of a radioactive source has fallen to $\tfrac{1}{32}$ of its original value. How many half-lives have elapsed? If the half-life is $4\,\text{years}$ , what is the total elapsed time?
Step-by-step solution
1. Step 1
  $\tfrac{1}{32} = \left(\tfrac{1}{2}\right)^{n}$ . Since $2^{5} = 32$ , $n = 5$ .
2. Step 2
  Total time $= n \times t_{1/2}$ .
  $t = 5 \times 4 = 20\,\text{years}$
Answer
$5$ half-lives → $20\,\text{years}$ .
10Carbon-14 dating
Extended• dating, C-14
Question
A piece of charcoal from an archaeological site has $\tfrac{1}{8}$ the carbon-14 activity of fresh wood. The half-life of $^{14}\text{C}$ is $5700\,\text{years}$ . Estimate the age of the charcoal.
Step-by-step solution
1. Step 1
  $\tfrac{1}{8} = \left(\tfrac{1}{2}\right)^{3}$ , so $n = 3$ half-lives have elapsed.
2. Step 2
  Age $= n \times t_{1/2}$ .
  $t = 3 \times 5700 = 17\,100\,\text{years}$
Answer
$\approx 17\,100\,\text{years}$
11Why a medical tracer must have a short half-life
Challenge• safety, tracer
Question
Technetium-99m is widely used as a medical tracer. Its half-life is about $6\,\text{hours}$ and it emits only $\gamma$ radiation. Explain why each of these properties is important for safe medical use.
Step-by-step solution
1. Step 1
  Short half-life ( $6\,\text{hours}$ ) → activity in the patient falls rapidly, so the radiation dose to surrounding healthy tissue is limited. After about a day ( $\sim 4$ half-lives) the activity is below $\tfrac{1}{16}$ of its initial value.
2. Step 2
  Pure $\gamma$ emission → the radiation penetrates tissue and is detected OUTSIDE the body for imaging. It does NOT deposit large amounts of energy in tissue per unit pathlength (unlike $\alpha$ ), so biological damage is minimised.
3. Step 3
  However, the half-life must not be TOO short, or the tracer would decay before the imaging scan is complete. $6\,\text{hours}$ is the practical compromise.
Answer
Short half-life limits dose to the patient; pure $\gamma$ allows external detection while causing minimal tissue damage; $6\,\text{hours}$ is long enough for the scan and short enough to clear quickly.
Examiner tip
The examiner report flags candidates often saying 'shorter is always safer' — too short a half-life makes the source useless before the scan is finished. The half-life must MATCH the time scale of the procedure.
12Deflection of $\alpha$ vs $\beta$ in an electric field
Challenge• deflection, field
Question
A beam of $\alpha$ particles and a beam of $\beta$ particles travel into the same uniform electric field at the same speed. Compare the direction and magnitude of their deflections.
Step-by-step solution
1. Step 1
  $\alpha$ has charge $+2e$ and mass $\approx 4\,\text{u}$ . $\beta^{-}$ has charge $-e$ and mass $\approx 1/1836\,\text{u}$ .
2. Step 2
  Direction: $\alpha$ deflects towards the NEGATIVE plate; $\beta$ deflects towards the POSITIVE plate (opposite directions).
3. Step 3
  Magnitude: acceleration $= F/m = qE/m$ . Compare $(qE/m)_{\beta} / (qE/m)_{\alpha} = (1/m_{\beta}) \times (1/(2/m_{\alpha})) \approx \tfrac{m_{\alpha}}{2 m_{\beta}}$ . Since $m_{\alpha} \approx 7300 \, m_{\beta}$ , the $\beta$ deflection is roughly $3500 \times$ greater.
Answer
$\alpha$ deflects towards the $-$ plate; $\beta$ deflects towards the $+$ plate, in the opposite direction. The $\beta$ deflection is much LARGER because of its tiny mass.

Key Formulae — Radioactivity

The formulae you need to memorise for radioactivity on the Cambridge IGCSE 0625 paper, with every variable defined in plain English and a note on when to use it.

Activity after $n$ half-lives
$A = A_{0} \left(\dfrac{1}{2}\right)^{n}$
$A_{0}$
initial activity (Bq)
$n$
number of half-lives elapsed = $t / t_{1/2}$
When to use
Predicting remaining activity / number of nuclei after a known time.
Conservation in nuclear equations
$\Sigma A_{\text{LHS}} = \Sigma A_{\text{RHS}};\ \Sigma Z_{\text{LHS}} = \Sigma Z_{\text{RHS}}$
When to use
Balance any decay or reaction equation.

Key Definitions and Keywords — Radioactivity

Definitions to memorise and the exact keywords mark schemes credit for radioactivity answers — sharpened from recent examiner reports for the 2026 0625 sitting.

Radioactive decay
Examiner keyword
Spontaneous, random emission of $\alpha$ , $\beta$ or $\gamma$ radiation by an unstable nucleus.
Alpha ( $\alpha$ ) particle
Examiner keyword
Helium-4 nucleus: $^{4}_{2}\text{He}$ . Charge $+2$ , heaviest of the three.
Beta ( $\beta^{-}$ ) particle
Examiner keyword
High-energy electron emitted from the nucleus. Charge $-1$ .
Gamma ( $\gamma$ ) ray
Examiner keyword
High-energy electromagnetic wave emitted from an excited nucleus. No charge or mass.
Half-life
Examiner keyword
Time taken for the activity (or number of undecayed nuclei) to fall to half its initial value.
Becquerel (Bq)
Examiner keyword
$1\,\text{Bq}$ = one decay per second.

Common Mistakes and Misconceptions — Radioactivity

The traps other students keep falling into on radioactivity questions — taken from recent Cambridge IGCSE 0625 examiner reports and mark schemes — and how to avoid them.

✕Reading half-life from one specific point on the graph
0625/42 — recurring
Why it happens
Treating the curve as linear.
How to avoid it
Half-life is constant: take an average from MULTIPLE drops (e.g. $1000 \to 500$ , $500 \to 250$ ).
✕Failing to balance $A$ AND $Z$
Why it happens
Only checking the mass number.
How to avoid it
BOTH $A$ and $Z$ must balance on every nuclear equation.
✕Saying $\alpha$ is an EM wave
Why it happens
Confusing with $\gamma$ .
How to avoid it
$\alpha$ = helium NUCLEUS (matter). Only $\gamma$ is EM.
✕Saying decay is caused by temperature or pressure
Why it happens
Comparing to chemical reactions.
How to avoid it
Radioactive decay is SPONTANEOUS and RANDOM — independent of physical conditions.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Video lesson

Short walkthrough of the concepts students most often get stuck on.

Radioactivity — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Property

Alpha (

\alpha

)

Beta (

\beta^{-}

)

Gamma (

\gamma

)

Identity

Helium-4 nucleus,

^{4}_{2}\text{He}

High-energy electron,

^{0}_{-1}\text{e}

EM wave (photon)

Charge

+2

-1

0

Mass

\approx 4\,\text{u}

\approx 1/1836\,\text{u}

0

Speed

\sim 5\%

of light

Up to

\sim 99\%

of light

Speed of light

Ionising power

HIGH

Medium

LOW

Penetrating power

Low

Medium

High

Stopped by

Paper, skin,

\sim 5\,\text{cm}

air

Few mm aluminium

Thick lead / concrete

Deflected by E or B field?

Yes (slightly,

+ve

)

Yes (more,

-ve

)

Sources of background radiation.

Cosmic rays from space.
Radon gas from rocks (especially granite).
Food and drink (e.g. potassium-40).
Medical (X-rays, radiotherapy).
Nuclear power & weapons fallout (small).

When measuring an experimental sample's activity, ALWAYS subtract background activity from the measured value.

Uses.

Smoke detectors (alpha source, americium-241): smoke disrupts an ionised current → alarm.
Cancer treatment (gamma): targeted gamma kills tumour cells.
Sterilising medical equipment with gamma.
Tracers in medicine (small, short half-life iodine for thyroid imaging).
Carbon dating (carbon-14 half-life of 5730 years).
Industrial thickness measurement with beta sources (changing thickness changes count rate).
Smoke detectors and alarms.

Dangers.

Ionising radiation damages DNA → mutation, cancer.
Acute high doses cause radiation sickness, organ failure, death.
Long-term low-dose exposure can be cumulative.

Safety precautions.

Distance: more distance = lower intensity (inverse-square).
Shielding: lead aprons, concrete walls, soil cover.
Time: limit exposure duration.
Containment: store sources in lead-lined boxes, use tongs.

Choosing the right radiation for the job.

Alpha: only useful inside the body (medical) where its high ionising power kills targeted cells. Don't use alpha for diagnostic imaging since it doesn't escape the body.
Beta: thickness gauges, medical tracers (β source needs to leave the body for detection).
Gamma: most penetrating, best for sterilising and cancer treatment outside the body.

Radioactivity

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1Compare α\alphaα, β\betaβ and γ\gammaγ

2Balance an α\alphaα decay

3Balance a β−\beta^{-}β− decay

4Half-life calculation

5Identify a radiation from penetration

6Match radiation to application

7Background-radiation correction

8Read half-life off a decay graph

9How many half-lives have passed?

10Carbon-14 dating

11Why a medical tracer must have a short half-life

12Deflection of α\alphaα vs β\betaβ in an electric field

Activity after nnn half-lives

Conservation in nuclear equations

Radioactive decay

Alpha (α\alphaα) particle

Beta (β−\beta^{-}β−) particle

Gamma (γ\gammaγ) ray

Half-life

Becquerel (Bq)

✕Reading half-life from one specific point on the graph

✕Failing to balance AAA AND ZZZ

✕Saying α\alphaα is an EM wave

✕Saying decay is caused by temperature or pressure

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

Radioactivity — frequently asked questions

Radioactivity

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1Compare α\alphaα, β\betaβ and γ\gammaγ

2Balance an α\alphaα decay

3Balance a β−\beta^{-}β− decay

4Half-life calculation

5Identify a radiation from penetration

6Match radiation to application

7Background-radiation correction

8Read half-life off a decay graph

9How many half-lives have passed?

10Carbon-14 dating

11Why a medical tracer must have a short half-life

12Deflection of α\alphaα vs β\betaβ in an electric field

Activity after nnn half-lives

Conservation in nuclear equations

Radioactive decay

Alpha (α\alphaα) particle

Beta (β−\beta^{-}β−) particle

Gamma (γ\gammaγ) ray

Half-life

Becquerel (Bq)

✕Reading half-life from one specific point on the graph

✕Failing to balance AAA AND ZZZ

✕Saying α\alphaα is an EM wave

✕Saying decay is caused by temperature or pressure

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

Radioactivity — frequently asked questions

1Compare $\alpha$ , $\beta$ and $\gamma$

2Balance an $\alpha$ decay

3Balance a $\beta^{-}$ decay

12Deflection of $\alpha$ vs $\beta$ in an electric field

Activity after $n$ half-lives

Alpha ( $\alpha$ ) particle

Beta ( $\beta^{-}$ ) particle

Gamma ( $\gamma$ ) ray

✕Failing to balance $A$ AND $Z$

✕Saying $\alpha$ is an EM wave

1Compare $\alpha$ , $\beta$ and $\gamma$

2Balance an $\alpha$ decay

3Balance a $\beta^{-}$ decay

12Deflection of $\alpha$ vs $\beta$ in an electric field

Activity after $n$ half-lives

Alpha ( $\alpha$ ) particle

Beta ( $\beta^{-}$ ) particle

Gamma ( $\gamma$ ) ray

✕Failing to balance $A$ AND $Z$

✕Saying $\alpha$ is an EM wave