Transcript P2 - Powerpoint

Monday, 11 April 2016
Unit P2 - Radiation
Lesson 01 – Introduction to Radiation
Aims:
•
Know that radiation is
produced from the nucleus of
the atom
•
Know that there are three
different types of nuclear
radiation
Questions…
1. What particles make up
atoms?
It comes
from…
Sources of background Radiation
copy
Sources of Background Radiation
Source
Amount
Radon Gas from Granite
51 %
The ground
14 %
Food & Drink (coffee &
peanuts)
12 %
Cosmic Rays (outer space)
10 %
Medical (X-Rays etc.)
12 %
Other (including nuclear
power stations)
1%
In the South West,
radon gas is a major
contributor to
background
radiation.
This is more evident
in enclosed spaces
e.g. caves and
granite houses on
Dartmoor
You are exposed to
a lot more cosmic
radiation on a flight.
What happens when radiation
reaches atoms and cells?
• Alpha (α) and beta (β) cause
ionisation – the radiation
removes electrons from atoms.
• This makes the atoms very
reactive
• It makes atoms react
uncontrollably making strange
substances
• It makes cells faulty – possibly
causing cancer
• The higher the dose of
radiation – the greater chance
of damage / cancer
• Most gamma radiation passes
through people and does not
cause much damage
copy
•
•
•
•
What happens when radiation
reaches atoms and cells?
Alpha (α) and beta
(β) cause ionisation
– the radiation
removes electrons
from atoms.
This makes the
atoms very reactive
and can…
It makes cells faulty
– causing cancer
The higher the dose
of radiation – the
greater chance of
damage / cancer
copy
It is detected
by…
Geiger counter
Demo Geiger
counter
Do some
work…
There are
three main
types of
Radiation
Radiation – a few facts…
• The nucleus of atoms is made
from protons and neutrons
• Radiation comes from the
nucleus of atoms
• There are three types of
radiation
 Alpha
 Beta
 Gamma
α
β
γ
αβγ
Alpha Decay…
• Phosphorous atom
(15 protons)
Proton
Neutron
Electron
Nucleus becomes unstable…
• Phosphorous atom
(15 protons)
Proton
Neutron
Electron
A group of 2 protons and 2
neutrons ejected…
• Phosphorous atom
(15 protons)
The group of 2 protons and two
neutrons is called an ALPHA
particle
It shoots out at high speed
straight past the electrons
Proton
Neutron
Electron
Alpha particle…
A group of 2 protons and 2
neutrons ejected…
The phosphorous atom has lost 2
protons (it now has 13)
It is now an Aluminium atom
Proton
Neutron
Electron
Beta Decay…
• Phosphorous atom
(15 protons)
Proton
Neutron
Electron
Beta Decay…
• Neutrons are made from
a proton and an electron
(& an anti-neutrino)
Proton
Neutron
Electron
Beta Decay…
• A neutron becomes
unstable, it splits up
and ejects the
electron at high
speed. (the anti-nutrino is
ejected)
• The proton stays in
the nucleus
Proton
Neutron
Electron
Gamma Decay
• When alpha or beta
radiation is produced
excess energy is
released as a gamma ray
• Gamma rays are not
particles
• Gamma rays are part of
the electromagnetic
spectrum
Types of Radiation
Unstable
nucleus
Unstable
nucleus
Unstable
nucleus
New
nucleus
New
nucleus
New
nucleus
Alpha
particle
1) Alpha () – an atom decays into a
new atom and emits an alpha particle
(2 protons and 2 neutrons – the
nucleus of a helium atom)
2) Beta () – an atom decays into a
new atom by changing a neutron into a
proton and electron. The fast moving,
Beta particle high energy electron is called a beta
particle.
Gamma
radiation
3) Gamma – after  or  decay surplus
energy is sometimes emitted. This is
called gamma radiation and has a very
high frequency with short wavelength.
The atom is not changed.
Copy this bit…
Ionisation
When radiation collides with neutral atoms or molecules it
alters their structure by knocking off electrons. This will leave
behind IONS – this is called IONISING RADIATION.
 particle
Electron
Different
radiation is
stopped by a
different
material
Radioactivity
If a substance is capable of ALWAYS emitting radiation under any conditions we
say it is ____________. There are three types of radiation: ALPHA, _____ and
GAMMA. These types of radiation are always given off by rocks, _____,
building materials, air and cosmic rays around us – this is called
BACKGROUND RADIATION. Each type is capable of penetrating different
materials:



Sheet of
paper
Few mm of
_________
Few cm of
lead
Words – aluminium, beta, food, radioactive
Properties of alpha, beta and
gamma radiation…
Name of
radiation
Symbol Passes
through:
Is absorbed by:
Alpha
α
5cm air only
A few cm of air
Beta
β
Air & paper
A thin sheet of
paper
Gamma
γ
Most things
A thick sheet of
except thick lead lead
and concrete
A very thick wall of
concrete
Task…
1. Use longman FND
book 2 – Page 234
2. Produce three bubble
map showing the
properties of alpha,
beta and gamma
radiation.
3. Then, produce a
‘double bubble’ map
showing comparing
and contrasting the
properties of alpha
and beta radiation
Alpha
Alpha
Beta
Questions…
Longman FND page 234-235.
Questions 1-6 & Summary
Homework…
Worksheet L15.1
Monday, 11 April 2016
1.
2.
3.
4.
5.
6.
7.
How can concrete protect people from
gamma radiation?
What types of radiation are stopped by a
thin sheet of aluminium?
Polonium-210 is very radioactive, it emits
alpha particles and glows blue. Explain why
is safe to store 210Po in a paper bag.
(http://en.wikipedia.org/wiki/Polonium)
What is background radiation?
Why is an alpha particle sometimes
referred to as a helium nucleus?
Alpha and beta radiation can be deflected
by a magnetic or electric field. Gamma
radiation cannot be deflected by electric or
magnetic fields – explain why.
If alpha radiation was deflected upwards by
a magnetic field, what way would beta be
deflected. Explain your answer
Lesson 4
Directing
Radiation
Recap
• What are the three types of
radiation?
• Match the radiation with its
properties...
Alpha
An
energy
beam
• Where does radiation come
from?
• Name some sources of
radiation?
• Why do we [in Plymouth] get
more radiation than people in
other parts of the country?
• Describe the process that
makes beta radiation.
Beta
Two
protons
and two
neutrons
Gamma
A fast
moving
electron
Radiation can
be deflected
by a
magnetic
field
Properties of alpha, beta and
gamma radiation…
Name of
radiation
Symbol Passes
through:
Is absorbed by:
Alpha
α
5cm air only
A few cm of air
Beta
β
Air & paper
A thin sheet of
paper
Gamma
γ
Most things
A thick sheet of
except thick lead lead
and concrete
A very thick wall of
concrete
Things to do...
• Complete the handout with the
properties of alpha, beta and gamma
radiation
• Use Longman FND book2, Btec
Science book or the AQA book to
help
Aluminium Rollers
Match the radiation
Alpha
Electromagnetic
radiation
Stopped by
paper or skin
Beta
High energy
electron
Reduced by
lead
Gamma
Helium
nuclei
Stopped by
aluminium
Background radiation
Background radiation is the radiation all around us.
Working in pairs try to think of five possible
sources of background radiation.
You have FIVE minutes!!
Rocks
Air
Building materials
Outer space
Food
The penetration power of the three types
of radiation.



Thin mica
Skin or paper
stops ALPHA
Thin aluminium
stops BETA
Thick lead
reduces GAMMA
Using your results from the previous three
investigations, fill in the table below:
Alpha
Beta
Gamma
Penetrating power
least
medium
most
Range of radiation
shortest
medium
longest
Most dangerous
outside of body
least
medium
most
Most dangerous
inside of body
most
medium
least
Affected by a
magnetic field
yes
yes
no
Thickness Control Mill
If not
A
radioactive
enough
source is on is
radioactivity
one
side of the
detected
then
material
the
rollers
and a
detector ontothe
compress
other. the
make
material thinner.
If too much
radioactivity
This
method is
is
getting
used
in through,
the
then the material
manufacture
of
is too
lots
ofthin
sheet
and
the rollers open
materials:
up a bit to
plastics,
paper,
make
the material
sheet
steel.
thicker.
Beta Source
detector
Hydraulic
ram
Electronic instructions to adjust rollers.
Assessment – Aluminium
Rollers
Scenario:
You need to write a sales pitch trying to
sell a new Aluminium
rolling machine and sensor to an
Aluminium Factory
e.g.
http://www.mettradeindia.com/index.php
Assessment... (P2)
AQA
Lng 2 Btec
What you must do to Pass this assignment...
378
(240)

Explain how a Aluminium Roller works (AQA page
378 may help)
234

Work out which would be the most appropriate
radiation to use to work out the thickness of the
Aluminium (explain what alpha, beta and gamma
are, which you would choose and why)

Write down everything you have found out from the
theory about alpha, beta and gamma. (What they
are, their range, their levels of ionisation, what you
need to stop them etc.)
234

Find out what the maximum thickness of Aluminium
you could produce and measure by this method
you could use
234

Find out what radioactive source you would use for
(a) Paper, (b) thick card, (c) lead
234

You must describe the properties of the radiation
and why it is stopped by the materials above
374,
383
234
42