Transcript Radiation True or False?

Radiation True or False?
1. You are being bombarded with radiation right now.
2. You are giving off radiation right now
3. Your breakfast was irradiated with deadly radiation
4. You can see radioactivity
5. You can feel radioactivity
True
True
True ??
False
False
6. Radioactive substances are only harmful if you touch them
7. If you are irradiated then you become radioactive
8. Radioactivity is not very useful
9. We completely understand what causes radioactivity
10. Do you know the three types of radioactivity. Write them
down..
False
False
False
False
?
PM S5 K1: Distinguish between stable and
radioactive isotopes and describe the conditions
under which the nucleus is unstable.
Alpha radiation - 
Description:
2 neutrons, 2 protons (helium nuclei)
Electric Charge:
+2
Relative Atomic Mass:
4
Penetration power:
Stopped by paper or a few cm of air
Helium nuclei
?
Ionisation effect:
Strongly ionising
Effects of Magnetic/Electric Field:
Weakly deflected
Beta radiation - 
Description:
High energy electron
Electric Charge:
-1
Relative Atomic Mass:
1/1860th
high energy electron
Penetration power:
Stopped by few mm of aluminium
Ionisation effect:
Weakly ionising
Effects of Magnetic/Electric Field:
Strongly deflected
Gamma radiation - 
Description:
High energy electromagnetic radiation
Electric Charge:
0
Relative Atomic Mass:
0
Penetration power:
Electromagnetic radiation
Reduced by several cms of lead or
several metres of concrete
Ionisation effect:
Very weakly ionising
Effects of Magnetic/Electric Field:
NO deflection
Let’s have a look at some radioisotopes.
Think about how we may be able to use them!
The penetration power of the three types
of radiation.



Thin mica
Skin or paper
stops ALPHA
Thin aluminium
stops BETA
Thick lead
reduces GAMMA
So what exactly does cause this radiation? .
First we need to look at the structure of the atom
Draw diagrams to represent:
How did you go?
6 protons
6 protons
6 protons
6 neutrons
7 neutrons
8 neutrons
6 electrons
6 electrons
8 electrons
What do we call these?
6 protons
6 protons
6 protons
6 neutrons
7 neutrons
8 neutrons
6 electrons
6 electrons
8 electrons
Isotopes
Atoms of the same element with different numbers of
neutrons
Isotopes
Atoms of the same element with different numbers of
neutrons
Because they have the same number of electrons there is NO
difference to their chemical behaviour.
Stable and unstable Isotopes
There are over 2000 different isotopes that have been
discovered so far.
Only 279 are stable – they do not emit radiation.
The rest are unstable and are called radioisotopes
The nuclei rearrange to become more stable.
As they do so they emit radiation.
But which ones are unstable?
Lets have a look at some of these isotopes.
Stable and unstable Isotopes
So why are some nuclei unstable?
Some nuclei are unstable because of the proton to
neutron ratio.
For light elements, stable nuclei have a
proton:neutron ration close to 1:1.
For heavy elements the stable nuclei have a
proton:neutro ratio close to 1:1.5
Stable and unstable Isotopes
p= n
Uses of radiation
Thickness Control Mill
radioactive
IfAnot
enough
source is onisone
radioactivity
side of the
detected
then
material
the
rollersand a
detector on
compress
to the
other.the
make
material thinner.
If too much
radioactivity
is
This
method is
getting
through,
used
in the
then the material
manufacture
of
is too
thin and
lots
of sheet
the rollers open
materials:
up a bit paper,
to make
plastics,
the material
sheet
steel.
Hydraulic
thicker.
ram
Beta Source
detector
Electronic instructions to adjust rollers.
Leak detection in pipes
The radioactive isotope is injected into the pipe. Then the
outside of the pipe is checked with a Geiger-Muller detector,
to find areas of high radioactivity. These are the points
where the pipe is leaking. This is useful for underground
pipes that are hard to get near.
The isotope must
have a short half life
so the material does
not become a long
term problem.
The radioactive isotope must be a gamma emitter so that it can be
detected through the metal and the earth where the pipe leaks.
Alpha and beta rays would be blocked by the metal and the earth.
Cobalt-60 Sterilisation
Gamma rays are used to kill bacteria, mould and insects in ood.
Also used to kill bacteria on hospital equipment.
This is useful particularly on packaged food or on plastic items
which would be damaged by heat sterilisation.
It can affect the taste and the vitamin content, but it lengthens the
shelf life.
unsterilised
Gamma Source
sterilised
Sterilisation
Cobalt-60 is used as it is a gamma emitter – very penetrating.
It has a half life of 5.3 years so the machines can run cheaply without
regular maintenance.
You don’t need external power to produce the gamma rays as you do
with x-rays
Cobalt-60 is held in a chemically inert form in a sealed container.
When the cobalt-60 is exhausted it can easily be replaced.
unsterilised
Gamma Source
sterilised
Radioactive half-life
The average time taken for half of the substance to decay is
called the radioactive half-life.
Carbon 15 / g
Decay of carbon 15
10
8
6
4
2
0
0
1
2
3
4
5
6
Time / s
7
8
9
10
Radioactive half-life
What is the half life of Carbon-15?
Carbon 15 / g
Decay of carbon 15
10
8
6
4
2
0
0
1
2
3
4
5
6
Time / s
7
8
9
10
PM S5 K5 – Identify one use of a named
radioisotope:
in industry
In medicine
PM S5 K6 – Describe the way in which the above
named industrial and medical isotopes are used
and explain their use in terms of their chemical
properties.
(This is your homework – ask for a handout!
Include something about half life in your answers.)
Start by reading p98-101.
Cobalt-60 and Technetium 99 are easy to research
but it is entirely up to you.
Think about this!
What happens if radiation is incident upon a living cell?
Radiation can ionise cells which
causes cellular damage.
If the exposure is high, it can kill the cell.
If the exposure is lower it can
cause cancer.
The higher the exposure, the higher the
risk of cancer.
PM S5 P6 – Use available evidence to analyse
benefits and problems with the use of radioactive
isotopes in industries and medicine
Read p98 and from what you have learnt today make a list
of benefits.
Read p 101 and from what you have learnt today make a
list of problems.
PM S5 P6 – Use available evidence to analyse
benefits and problems with the use of radioactive
isotopes in identified industries and machines.
Benefits:
Problems:
•Non-invasive diagnostic
procedures
•Tissue damage for people
exposed
•Treatement of cancers
•Risk of cancer if exposed
•Sensitive monitoring of
inductrial processes
•Genetic damages to
people exposed
•Sterilisation
•Hard to dispose of some
isotopes (long half-life)
•Non-invasive examination
of pipes / aircraft etc.