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What do you think of radiation?


What is ‘radiation’?

The term radiation (also known as nuclear radiation) refers to the particles or waves emitted by radioactive substances.

proton

neutron

electron

An atom has electrons orbiting the outside and a central nucleus, which is made up of protons and neutrons.

Nuclear radiation comes from the nucleus of a radioactive atom.

In a radioactive atom, the nucleus is unstable and so it emits particles or waves to form a more stable atom.

This process is called radioactivity or radioactive decay. It is a natural and completely spontaneous process.


How can radiation be detected?

Radiation is all around us – naturally occurring, and man-made sources, but it is invisible, so how do we actually know it’s there?

The effects of radiation can be seen and so it can detected using instruments such as a Geiger-Müller tube.

This is a device that can detect and measure radiation.

Radioactivity can also be detected by the presence of photographic film, which darkens when struck by radiation. This effect lead to the initial discovery of radioactivity more than one hundred years ago.


The discovery of radioactivity


What is radioactive decay?


How do materials affect radiation?


How do magnetic fields effect radiation?


Description

What is alpha (α) radiation?

Electric charge +2

Relative atomic mass 4

Penetrating power Stopped by paper or a few centimetres of air

Ionizing effect Strongly ionizing

Effect of magnetic/ electric field Weakly deflected

2 neutrons, 2 protons

Note:– An alpha particle is the same as a helium nucleus


What is beta (β) radiation?

Description

Electric charge

Relative atomic mass

Penetrating power

Ionizing effect

Effect of magnetic/ electric field

-1

1/1860

Stopped by a few millimetres of aluminium

Weakly ionizing

Strongly deflected

High energy electron


Gamma () radiation

Description

Electric charge

Relative atomic mass

Penetrating power

Ionizing effect

Effect of magnetic/ electric field

0

0

Stopped by several centimetres of lead or several metres of concrete

Very weakly ionizing

Not deflected

High energy electromagnetic radiation


Types of radiation and penetrating power


Types of radiation and range in air


What is radiation used for?


Smoke alarms contain a weak source of alpha radiation.

How can radiation detect a fire?

The alpha particles ionize the air.

If there is smoke present, it interacts with the ions produced by the alpha particles and ionization is reduced.

This means that less current is flowing through the air, which causes the alarm to sound.

α

α

smoke particle


How is radiation used in making paper?


How can radiation find leaks in pipes?


How can radiation detect cracks?

Gamma rays can also be used to detect cracks after an object has been welded.

If a gamma source is placed on one side of the welded metal, and a photographic film on the other side, any flaws will show up on the film like an X-ray.

Gamma rays are like X-rays.

welded metal pipe

photographic film

welding flaws


Gamma rays are used to kill bacteria, mould and insects in food.

Gamma rays are also used to kill bacteria on medical equipment.

How is radiation used for sterilization?

This can be done even after the food has been packaged. It can affect the taste, but supermarkets like it because it lengthens the shelf life.

It is particularly useful with plastic equipment that would be damaged by heat sterilization.


Uses of radiation – activity


Dangers of ionizing radiations


Dangers of ionizing radiations – activity


As well as the normal laboratory safety rules you follow, are there any extra rules concerning radioactivity?

Radiation safety

The three types of radiation differ in their effects and physical nature.

All radioactive sources must be handled safely.

The hazard symbol for radiation is shown below:


Radioactive materials could be very dangerous to handle if no safety precautions were taken.

How are radioactive sources used safely?

use tongs or a robotic arm to handle radioactive materials.

keep exposure times as short as possible monitor exposure with a film dose badge label radioactive sources clearly

store radioactive sources in shielded containers

wear protective clothing

The safety precautions are:

This is because people and their clothing could become contaminated.


Background radiation is the radiation all around us.

Background radiation

How many different sources of background radiation can you think of?

Most of the radioactivity you are exposed to is from natural sources.


Calculating background radiation


alpha radiation – Positively charged particles made up of two protons and two neutrons.

background radiation – Constant low-level radiation from food and environmental sources.

beta radiation – High-energy electrons emitted by some radioactive materials.

gamma radiation – Short-wavelength electromagnetic radiation emitted during radioactive decay.

Geiger-Müller tube – A device used to detect and measure radiation from radioactive materials.

ionizing radiation – High-energy radiation capable of ionizing substances through which it passes.

radioactivity – The spontaneous emission of radiation from the nucleus of an unstable atom.

Glossary


Anagrams


Multiple-choice quiz

1 of 34© boardworks ltd 2006. 2 of 34© boardworks ltd 2006

Documents

types of radiation

nuclear radiation

air slide

term radiation

measure radiation

beta radiation

effects of radiation

penetrating power slide