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What do you think of radiation?
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What is ‘radiation’?
The term radiation (also known as nuclear radiation) refers
to the particles or waves emitted by radioactive substances.
Nuclear radiation comes from the
nucleus of a radioactive atom.
electron
An atom has electrons orbiting
the outside and a central
nucleus, which is made up of
protons and neutrons.
proton
neutron
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.
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How can radiation be detected?
Radiation is all around us – naturally occurring, and manmade 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.
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The discovery of radioactivity
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What is radioactive decay?
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How do materials affect radiation?
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How do magnetic fields effect radiation?
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What is alpha (α) radiation?
Description
2 neutrons, 2 protons
Note:– An alpha particle is the
same as a helium nucleus
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
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What is beta (β) radiation?
Description
High energy electron
Electric charge
-1
Relative atomic mass 1/1860
Penetrating power
Stopped by a few millimetres
of aluminium
Ionizing effect
Weakly ionizing
Effect of magnetic/
electric field
Strongly deflected
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Gamma () radiation
Description
High energy electromagnetic
radiation
Electric charge
0
Relative atomic mass 0
Penetrating power
Stopped by several centimetres of
lead or several metres of concrete
Ionizing effect
Very weakly ionizing
Effect of magnetic/
electric field
Not deflected
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Types of radiation and penetrating power
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Types of radiation and range in air
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What is radiation used for?
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How can radiation detect a fire?
Smoke alarms contain a weak source of alpha radiation.
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.
smoke
particle
α
This means that less current is
flowing through the air, which
causes the alarm to sound.
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How is radiation used in making paper?
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How can radiation find leaks in pipes?
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How can radiation detect cracks?
Gamma rays can also be used
to detect cracks after an object
has been welded.
Gamma rays are like X-rays.
welded
metal pipe
welding flaws
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.
photographic film
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How is radiation used for sterilization?
Gamma rays are used to kill
bacteria, mould and insects in food.
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.
Gamma rays are also used to
kill bacteria on medical
equipment.
It is particularly useful with
plastic equipment that would be
damaged by heat sterilization.
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Uses of radiation – activity
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Dangers of ionizing radiations
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Dangers of ionizing radiations – activity
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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:
As well as the normal laboratory safety rules you follow, are
there any extra rules concerning radioactivity?
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How are radioactive sources used safely?
Radioactive materials could be very dangerous to handle
if no safety precautions were taken.
This is because people and their clothing could become
contaminated.
The safety precautions are:
 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
 use tongs or a robotic arm to
handle radioactive materials.
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Background radiation
Background radiation is the radiation all around us.
Most of the radioactivity you are exposed to is from natural
sources.
How many different sources of background radiation can you
think of?
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Calculating background radiation
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Glossary
 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.
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Anagrams
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Multiple-choice quiz
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