Alpha, beta and gamma radiation
Lesson objectives; You will learn:
1. The nature of alpha beta and gamma
2. The properties of alpha beta and gamma
3. Why these radiations are dangerous
STARTER ACTIVITY:
* List some Greek symbols and their meanings:
greek symbols

 
meanings
Alpha beta gamma
Pi theta delta omega
 
summation ohm wavelength

micro
Alpha, beta and gamma radiation
Types of radiation
Unstable
nucleus
New
nucleus
Alpha
particle
Beta
particle
Unstable
nucleus
Unstable
nucleus
New
nucleus
New
nucleus
Gamma
radiation
1) Alpha () – a nucleus decays into a
new nucleus and emits an alpha
particle (2 protons and 2 neutrons –
the nucleus of a helium atom)
2) Beta () – a nucleus decays into a
new nucleus by changing a neutron
into a proton and electron. The fast
moving, high energy electron is called
a beta particle.
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 nucleus is not
changed.
Alpha, beta and gamma radiation
Alpha, beta and gamma radiation
Alpha, beta and gamma radiation
Q1.
Why do Alpha and beta
deflect in opposite
directions?
Q2.
Why does gamma not
deflect in a
magnetic field?
Alpha, beta and gamma radiation
Ionization
An ion is a charged particle. Alpha , beta and gamma
radiations have the ability to ionize atoms when they
collide with them. The charged particles that are
created are potentially very dangerous - particularly if
they belong to your body!
This is the symbol for
radioactive materials
How does ionization happen?
Nucleus
(positively
charged)
An Atom
+
An electron
(negatively
charged)
-
Atoms are neutral as
they have equal
numbers of positive
and negative charges
How does ionization
happen?
An Atom
+
-
The charged particle left behind is called an
ion. We say that the atom has been ionized.
+
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
Why are ionizing radiations dangerous?
If they ionize atoms in living cells they can
cause the cells to mutate, and this can lead to
cancer.
Each time an atom is ionized the radiation
particle loses energy. They slow down and
eventually stop. At this point they are harmless as
they can do no more damage.
Alpha particles are strongly ionizing. They produce
many hundreds of ions per cm when they travel through
air. But this means they lose their energy quickly and
stop after a few cm.
Thin paper
Alpha
source
Where would these be
most dangerous?
Beta particles are less ionizing. They lose their
energy more slowly and can travel much further
in air than alpha particles.
Does this make
beta particles less
dangerous?
Thin paper
beta
source
Aluminium sheet
Gamma rays are not very ionizing. They travel
unimpeded through air. In fact, you need several
cm of lead or concrete to reduce their level, but
even then, a lot still get through.
Does this make them
less dangerous than
alphas and betas?
Thick lead
gamma
source
Alpha, beta and gamma radiation