Lesson plan

Topicm6b7469bdb4cb43af_1528449000663_0Topic

Nuclear radiationNuclear radiationNuclear radiation $α$ , $β$ and $γ$

Levelm6b7469bdb4cb43af_1528449084556_0Level

Second

Core curriculumm6b7469bdb4cb43af_1528449076687_0Core curriculum

XI. Nuclear physics. The student:

3) lists the properties of nuclear radiation; describes alpha, beta decays.

Timingm6b7469bdb4cb43af_1528449068082_0Timing

45 minutes

General learning objectivesm6b7469bdb4cb43af_1528449523725_0General learning objectives

Describes qualitatively alpha, beta and gamma decays.

Key competencesm6b7469bdb4cb43af_1528449552113_0Key competences

1. Lists the properties of nuclear radiation.

2. Describes the behavior of nuclear radiation in the electric field.

Operational (detailed) goalsm6b7469bdb4cb43af_1528450430307_0Operational (detailed) goals

The student:

- describes three types of nuclear radiationNuclear radiationnuclear radiation,

- lists the properties of nuclear radiation.

Methodsm6b7469bdb4cb43af_1528449534267_0Methods

1. Discussion.

2. Experiment.

Forms of workm6b7469bdb4cb43af_1528449514617_0Forms of work

1. Individual work.

2. Group work.

Lesson stages

Introductionm6b7469bdb4cb43af_1528450127855_0Introduction

Revision. The teacher asks the questions. The students draw a schematic diagram and write the basic concepts on the board.

What is an atom? What are atoms made of?

Procedurem6b7469bdb4cb43af_1528446435040_0Procedure

The teacher introduces the basic concepts of natural radioactivityradioactivityradioactivity.

Natural radioactivity:

All matter is made up of atoms. Atoms consist of electrons surrounding a nucleusnucleusnucleus. The nucleus consists of neutrons and protons. The nuclei of some atoms are unstable. These atoms (parent isotopes) decay spontaneously into more stable atoms (daughter isotope) and emit nuclear radiationNuclear radiationnuclear radiation. The substances emitting such radiation are called radioactive.

Types of radiation:

There are three types of nuclear radiation:

- alpha ( $α$ ),
- beta ( $β$ ),
- gamma ( $γ$ ).
$α$ , $β$ and $γ$ are the first letters of the Greek alphabet. The types of radiation are named in the order in which they were discovered.

[Illustration 1]

The students work in small groups and complete the tasks.

Task 1
Read the text below about properties of nuclear radiationNuclear radiationnuclear radiation. Rewrite to your notebook and fill in the table below.

[Table 1]

Alpha radiation:
Alpha particles are made up of 2 protons and 2 neutrons. They have a positive charge equal to twice the elementary charge and are identical to helium nuclei. Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation. They have low penetrating power and have a range of a few centimetres in air. They can be stopped with a sheet of paper.m6b7469bdb4cb43af_1527752263647_0Alpha radiation:
Alpha particles are made up of 2 protons and 2 neutrons. They have a positive charge equal to twice the elementary charge and are identical to helium nuclei. Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation. They have low penetrating power and have a range of a few centimetres in air. They can be stopped with a sheet of paper.

Beta radiation:
Beta particles have a negative charge equal to the elementary charge and a mass of about $\frac{1}{2000} - t h$ of a proton mass. This means that beta particles are electrons (or positrons) produced in the nucleus as a result of a radioactive decay called beta decay (they are not orbital electrons). They are very light and move fast. Beta radiation can penetrate air and paper. It can be stopped by a thin sheet of aluminium.m6b7469bdb4cb43af_1527752256679_0Beta radiation:
Beta particles have a negative charge equal to the elementary charge and a mass of about $\frac{1}{2000} - t h$ of a proton mass. This means that beta particles are electrons (or positrons) produced in the nucleus as a result of a radioactive decay called beta decay (they are not orbital electrons). They are very light and move fast. Beta radiation can penetrate air and paper. It can be stopped by a thin sheet of aluminium.

Gamma radiation:
Gamma rays are electromagnetic waves, not particles. They have no mass and no charge. Gamma rays have a high penetrating power. Low‑energy gamma rays can penetrate air, paper or thin metal. High‑energy gamma rays can only be stopped by a few centimetres of lead or a few meters of concrete.

[Illustration 2]

Penetrative properties of different types of radiation

IonisationionisationIonisation:

Nuclear radiationNuclear radiationNuclear radiation can ionise matter, that is, atoms of the medium are no longer electrically neutral. Charged particles interact strongly with atoms and ionise them directly (Coulomb interaction), knocking out the electron and the atomic shell and losing energy.

Alpha particles can ionise other atoms strongly because they have a large charge. Beta particles can ionise atoms, but weaker than alpha particles.

Gamma rays interact less with matter, having no electrical charge they ionize matter indirectly through other processes such as photoelectric effect or Compton scattering, where the released electrons have enough energy to be able to ionize matter as a result of Coulomb interaction. For this reason, the ability of gamma radiation to penetrate matter is the greatest.

Task 2
You already know some properties of alpha, beta and gamma radiation. How is the emission of alpha, beta and gamma particles affected by the electric field? Identify sources of radiation shown in the picture and justify your statement.

[Illustration 3]

Answer:

Source 1 – alpha source.
Source 2 – gamma source.
Source 3 – beta source.

Alpha particles carry positive charge. They are attracted by the negative plate and are less deflected then beta particles due to the greater mass. Gamma rays have no charge and are not deflected in the electric field. Beta particles are negatively charged and deflected towards the positive plate.

The teacher discusses the radiation detectiondetectiondetection methods.

DetectiondetectionDetection of radiation:

Nuclear radiation cannot be detected by human senses, so special equipment is necessary. The most common are personal dosimeters and Geiger‑Müller counters.

Personal dosimeters:
Film badges are the most known personal dosimeterdosimeterdosimeter in use. They are used to measure gamma, x‑ray, and high‑energy beta radiation. A badge consists of a small piece of photographic film wrapped in an opaque cover and held in a metal frame. Film badges are worn by people who work with radiation. Film badges monitor the levels of absorbed radiation. The photographic film goes dark when it absorbs radiation. The more radiation is absorbed, the darker is the film when it is developed in use. They are used to measure gamma, x‑ray, and high‑energy beta radiation. A badge consists of a small piece of photographic film wrapped in an opaque cover and held in a metal frame. Film badges are worn by people who work with radiation. Film badges monitor the levels of absorbed radiation. The photographic film goes dark when it absorbs radiation. The more radiation is absorbed, the darker is the film when it is developed.m6b7469bdb4cb43af_1527712094602_0Personal dosimeters:
Film badges are the most known personal dosimeterdosimeterdosimeter in use. They are used to measure gamma, x‑ray, and high‑energy beta radiation. A badge consists of a small piece of photographic film wrapped in an opaque cover and held in a metal frame. Film badges are worn by people who work with radiation. Film badges monitor the levels of absorbed radiation. The photographic film goes dark when it absorbs radiation. The more radiation is absorbed, the darker is the film when it is developed in use. They are used to measure gamma, x‑ray, and high‑energy beta radiation. A badge consists of a small piece of photographic film wrapped in an opaque cover and held in a metal frame. Film badges are worn by people who work with radiation. Film badges monitor the levels of absorbed radiation. The photographic film goes dark when it absorbs radiation. The more radiation is absorbed, the darker is the film when it is developed.

Geiger‑Müller counters:
The Geiger‑Müller counter is a gas‑filled tube, inside which there are two electrodes connected to a voltage of several hundred volts. Nuclear radiationNuclear radiationNuclear radiation passing through gas causes its ionization. The electrons and ions produced by ionization are accelerated in the electric field, causing further ionization processes and, as a result, an avalanche discharge. This is manifested by the creation of a electric current impulse, which is sent to a counting device. This device makes an acoustic sound or displays the count rate. The higher the sound frequency or the higher the counting rate, the higher the radiation.

Lesson summarym6b7469bdb4cb43af_1528450119332_0Lesson summary

There are three types of nuclear radiationNuclear radiationnuclear radiation: alpha ( $α$ ), beta ( $β$ ), gamma ( $γ$ ). Alpha and beta are charged particles while gamma rays are electromagnetic waves that don’t carry any charge. The most penetrating radiation are gamma rays, while beta radiation has smaller range and alpha particles can travel in air only a few centimetres. All three types of radiation can ionise matter.

Selected words and expressions used in the lesson plan

capacitorcapacitorcapacitor

detectiondetectiondetection

dosimeterdosimeterdosimeter

ionsationionisationionsation

Nuclear radiationNuclear radiationNuclear radiation

nucleusnucleusnucleus

penetratrionpenetrationpenetratrion

radioactivityradioactivityradioactivity

sourcesourcesource

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Nuclear radiation1

radioactivity1

nucleus1

ionisation1

capacitor1

detection1

dosimeter1

penetration1

source1

Scenariusz

Topicm6b7469bdb4cb43af_1528449000663_0Topic

Lesson stages

Selected words and expressions used in the lesson plan