Transcript Lesson 3 detection and background

Rayneritis!
Fill in the
summary
sheet on
Nuclear
radiation
Alpha, beta and gamma radiation
An alpha particle consists of two protons
and two neutrons.
It is strongly ionising.
A beta particle is a high speed electron.
It is produced when a neutron has decays into
an electron and proton.
It is moderately ionising.
Gamma rays are very high frequency
electromagnetic waves.
They are produced when an unstable nucleus
loses energy..
They are weakly ionising.
The penetrating power of
alpha, beta and gamma radiation
Paper or a few
cm of air stops
alpha particles
1cm or 1m of air
of aluminium
stops beta
particles
Several cm of lead or
1m of concrete is
needed to stop
gamma rays
Learning today
• The dangers of nuclear radiation
• What background radiation is
• How to detect radiation using
1.Photographic film
2.Geiger-Muller tube
3.Cloud chamber – alpha particles
Choose appropriate words to fill in the gaps below:
nucleus containing protons
Atoms consist of a very small _______,
and neutrons, surrounded by _______.
electrons Atoms of the same
protons but
element will always have the same number of _______
isotopes of the same element will have different
different ________
neutrons
numbers of _________.
radioactive
The atoms of some substances are unstable and _________.
beta particles or gamma rays.
They may give off alpha or ______
Gamma rays are the most penetrating type of radiation,
alpha is the least.
_____
WORD SELECTION:
alpha
beta
protons
electrons isotopes
nucleus neutrons radioactive
Safety
• Keep your
Distance
• Use tongs
• Use a lead apron or
screen
• Work with mechanical
robot arms
Fill in the note sheet
Dangers of radioactivity
Alpha
13/04/2015
Radiation will ionise atoms in living
cells – this can damage them and
cause cancer or leukaemia.
Beta
Gamma
Please
complete the
notes on the
dangers of
radiation
OUTSIDE the body  and  are
more dangerous as  radiation
is blocked by the skin.
INSIDE the body an  source
causes the most damage
because it is the most ionising.
It can enter as gas or dust.
Background radiation – Please
copy
Background radiation is
low-level ionising radiation
which is all around us
because of radioactive
material in the environment.
Most is natural but a small
amount is due to manmade sources such as
nuclear weapon testing.
Radon gas
Radon gas accounts for about 50% of
natural background radiation.
Two isotopes of radon, radon 222 and
radon 220 (also known as thoron) are
produced by the radioactive decay of
uranium and thorium in the Earth’s crust
.
This gas seeps into the atmosphere
sometimes building up first inside the
basements and foundations of buildings.
Areas containing granite and other
igneous rocks, for example Cornwall,
have a higher than average amount of
background radiation due to radon gas.
Background radiation map of
England and Wales
Cosmic rays
Cosmic rays are a form of natural
background radiation produced by the
nuclear reactions occurring in stars
and exploding stars called
supernovae.
These produce high energy particles
which continually bombard the Earth.
Our atmosphere gives us good
protection from cosmic radiation.
Cosmic radiation is an issue that must
be considered in proposed manned
space exploration to Mars.
Exposure to cosmic radiation is
increased during jet travel
Internal radiation
Internal radiation is background
radiation due to radioactive sources
present inside our bodies.
Some of these are from naturally
occurring events. An example is
carbon 14 that is formed in the
atmosphere by the Sun’s radiation.
This behaves chemically and
biologically in the same way as nonradioactive carbon 12.
Others such as strontium 90 are from
man-made events such as nuclear
weapons testing and accidents.
Strontium behaves like calcium in our
bodies.
We are all sources of
background radiation!
Artificial radiation
Artificial radiation is background
radiation due to man-made events or
procedures
Some is to due leakage and
accidents associated with the
generation of electricity using nuclear
energy. Some is due to fall-out from
nuclear weapon testing.
Radioactive tracers are used in
industry and medicine and
radioisotopes are used to treat
cancer.
Overall artificial radiation normally
accounts for only a small percentage
of background radiation.
The explosion of the
Chernobyl power plant in
the Ukraine in 19986
placed significant
radioactive isotope into
the atmosphere.
Background
radiation
Please
complete the
questions on
the sheet
Homework!
Complete
atomic
structure
crossword
Due Tuesday
18th
September
Detecting radioactivity – Fill in notes
Radioactivity can be
detected using
photographic film
or a Geiger counter or a
cloud chamber.
Radiation badge containing
photographic film
You need the word foggy
Geiger tube and counter
Radiation badges
Photographic film
darkens on exposure
to radiation and light.
Light cannot
penetrate the badge
but ionising radiation
can.
Darkening of the film
indicates that a
person has been
exposed to too much
radiation.
Engineer at CERN
wearing a radiation badge
The Geiger tube
Radiation produces ions in a low pressure gas between
a central positively charged electrode and the outer
negatively charged tube. A pulse of current then flows
that is registered by the counter.
The thin mica window allows the least penetrating
radiation (alpha) to enter the tube. Gamma radiation and
most beta can enter through the sides of the metal tube.
Cloud chamber
• Cloud chamber
• This is useful for
studying alpha
particles as they
make visible tracks in
the alcohol vapour
inside
Activity
The activity of a radioactive
source is equal to the number
of decays per second.
Activity is measured
in bequerels (Bq)
1 becquerel
= 1 decay per second
Henri Becquerel
discovered
radioactivity in 1896
Choose appropriate words to fill in the gaps below:
Becquerel
Radioactivity was first discovered by Henri ___________
in
1896 when he noticed that the radiation emitted by an ore of
uranium
photographic plate.
___________
caused the exposure of a _____________
Geiger
Radioactivity can also be detected using a _________
tube
counter or rate meter.
connected to an electronic _________
Background radiation is mainly due to natural sources of
ionising
_________
radiation such as from ________
gas that seeps
radon
out from rocks in the ground.
WORD SELECTION:
counter
radon
ionising
Geiger
photographic
Becquerel
uranium
Online Simulations
Build an atom - PhET - Build an atom out of protons, neutrons, and
electrons, and see how the element, charge, and mass change.
Then play a game to test your ideas!
Atom builder - Freezeway.com
Build an atom - eChalk
Types of Radiation - S-Cool section on types of radiations including an
animation of absorption and a couple of decay equations to fill in on
screen.
Decay series - Fendt
BBC AQA GCSE Bitesize Revision:
Atoms, isotopes & radioactivity - Core Science
Structure of an atom
Isotopes
Alpha, beta & gamma radiation
Penetration properties
Deflection radiation
Radioactive decay equations
Atoms and Radioactivity
1.
2.
3.
4.
5.
6.
Notes questions from pages 199 to 208
Describe the structure of an atom in terms of protons,
neutrons and electrons and explain the meaning of
symbols such as 146C.
Explain the meaning of (a) atomic number, (b) mass
number and (c) isotope.
What is alpha, beta and gamma radiation? Distinguish
between them in terms of their ionisation and
penetration powers.
Describe the changes that occur to a nucleus when it
undergoes alpha and beta decay. In each case give and
example of a decay equation.
Answer the questions on pages 207 and 208.
Verify that you can do all of the items listed in the end of
chapter checklist on page 207.