Lesson plan

Topicmb7a6c3cb06af667e_1528449000663_0Topic

Ionising radiation and its effect on living organisms

Levelmb7a6c3cb06af667e_1528449084556_0Level

Third

Core curriculummb7a6c3cb06af667e_1528449076687_0Core curriculum

XI. Nuclear physics. The student:

7) indicates the effect of ionising radiationradiationradiation on matter and on living organisms.

Timingmb7a6c3cb06af667e_1528449068082_0Timing

45 minutes

General learning objectivesmb7a6c3cb06af667e_1528449523725_0General learning objectives

Indicates the effect of ionising radiation on matter and on living organisms.

Key competencesmb7a6c3cb06af667e_1528449552113_0Key competences

1. Differentiates between non‑ionising and ionising radiation.

2. Describes various sources of ionising radiation.

Operational (detailed) goalsmb7a6c3cb06af667e_1528450430307_0Operational (detailed) goals

The student:

- describes how the ionising radiation interacts with matter,

- lists various sources of ionising radiation.

Methodsmb7a6c3cb06af667e_1528449534267_0Methods

1. Discussion.

2. Text analysis.

Forms of workmb7a6c3cb06af667e_1528449514617_0Forms of work

1. Individual work.

2. Group work.

Lesson stages

Introductionmb7a6c3cb06af667e_1528450127855_0Introduction

Revision. The teacher gives an input for discussion asking questions. The students summarize the results of discussion on the board.

What is radiation? What sources of radiation are present in our environmentenvironmentenvironment?

Proceduremb7a6c3cb06af667e_1528446435040_0Procedure

The teacher introduces the basic concepts of ionising and non‑ionising radiation.

Ionisation:
When a sufficient amount of energy is delivered to an atom, an electron can be removed from its orbit, leaving the atom ionized (atom is positively charged). Energy required to remove an electron from its orbit is in the range of 5‑20 eV. Ionisation is associated with the absorption of radiation.
If the incident energy is low, then the atom absorbs it and gets excited. When the atom comes back to the ground state, nonionizing radiation is emitted. Nonionizing radiation comes in the form of light, radio waves, microwaves and radar waves. These forms of radiation usually are not dangerous for human tissues, quite opposite to the ionizing radiation.

[Interactive graphics]

In living organisms exposed to radiationradiationradiation which energy is sufficient to induce ionisationionisationionisation the chemical bonds can be affected. Living organisms are able to correct damages caused by small amounts of radiation. But in case, when the radiation amount is large, the damages are huge and can lead to genetic defects, cancer or, in the worst case, to radiation sickness.

Sources of ionising radiation:

The origin of ionising radiation can be natural or artificial, caused through human activity. The effects of both kinds of ionisation are the same.

Natural sources of ionizing radiation:

- Radon:
Radon is a naturally occurring radioactive gas which is colorless and odorless. It is produced from the uranium that is present in rocks and soils, well water and building materials. Exposure to radon radiation increases the risk of lung cancer.

- Cosmic radiationradiationradiation:
High‑energy radiation from either the Sun (solar radiation) or from outside the Solar System (galactic radiation) are constantly passing through the Earth. This radiation is called cosmic radiation. Radiation doses from cosmic radiation are greater at higher altitudes. People who are often flying are getting higher doses of radiation.mb7a6c3cb06af667e_1527752256679_0High‑energy radiation from either the Sun (solar radiation) or from outside the Solar System (galactic radiation) are constantly passing through the Earth. This radiation is called cosmic radiation. Radiation doses from cosmic radiation are greater at higher altitudes. People who are often flying are getting higher doses of radiation.

- Natural radioactivity in soils:
Radionuclides of uranium, thorium and potassium are relatively abundant in rocks and soils. The gamma radiationradiationradiation emitted from these radionuclides gives us all a radiation dosedosedose.

- Thoron:
Thoron is a radon isotope, which is a naturally occurring radioactive gas. The main source of thoron in indoor air is building materials.

- Natural radioactivity in food:
All foods contain natural radioactivity, which is transferred from the soil to the plants on land, to animals eating these plants and from water to fish in rivers, lakes, seas and oceans.

[Illustration 1]

Artificial sources of ionizing radiation:

- Medical uses of radiation:
Many procedures in medical diagnosis involve exposure to radiation. The procedures that involve the use of radiation are: radiology, angiocardiograms, CT scans and nuclearnuclearnuclear medicine. All exposures to radiation used in medicine should be clinically justified.

- Radiation in the workplace:
People working with radioactive materials may receive a radiation dose. Such doses are usually very low.

- Radioactivity in the environmentenvironmentenvironment:
Radioactivity is also present in our environmentenvironmentenvironment due to nuclear weapons testing, accidents at nuclear facilities and radioactive wastes from nuclearnuclearnuclear and other facilities.

The students work in small groups and complete the tasks.

Task 1

Review the following sources of radiation and indicate where you might encounter them. Indicate whether the sourcesourcesource is non‑ionising radiation or ionising radiation.

[Table 1]

Answer:

[Table 2]

The students get familiar with units and quantities describing radiation.

RadiationradiationRadiation quantities and units:
There are different units and quantities for measuring radioactivity and its effects:

- Radioactivity (A) refers to the amount of ionizing radiation released by a radioactive material. This represents how many atoms in the material decay in a given time period. The SI unit is becquerel (Bq).

A = \frac{N}{t}

where:
N - a number of decays,
t - time,
$1 B q = \frac{1 r o z p a d}{1 s}$ .

- Exposure describes the amount of radiation travelling through the air. The unit is $\frac{coulomb}{kilogram}$ ( $\frac{C}{k g}$ ).

- Absorbed dosedosedose (D) refers to the amount of radiation absorbed by an object or person. The SI unit is gray (Gy):

D = \frac{E}{m}

where:
E - energy of radiation absorbed by the body,
m - mass of the body,
1 Gy = 1 $\frac{J}{k g}$ .

Historical unit of absorbed dose is rad, 1 Gy = 100 rad.

- Effective dose describes the amount of radiationradiationradiation absorbed by human tissues and organs. It takes into account the type and energy of radiation and its impact on particular organs. The SI unit is sievert (Sv).

[Illustration 3]

Task 2

One litre of seawater has an activity of 10 Bq.
Approximately how many nuclei decay every day in this quantity of seawater?

Answer:

$A = \frac{N}{t}$

$N = A \cdot t$

$N = 10 \cdot 60 \cdot 60 \cdot 24 = 864000 nuclei$

Lesson summarymb7a6c3cb06af667e_1528450119332_0Lesson summary

There are two types of radiation: ionising and non‑ionising. Non‑ionising radiation is usually harmless to living organisms while an exposure to ionising radiation can lead to severe damages in tissues.

Selected words and expressions used in the lesson plan

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Scenariusz

Topicmb7a6c3cb06af667e_1528449000663_0Topic

Lesson stages

Selected words and expressions used in the lesson plan