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Detecting Radioactivity using a Film Badge.
How can Radioactivity be Detected?
Radioactivity causes ionisation.
The ions formed can be
detected
using a photographic
film badge or a Geiger-Müller tube.
What is a Film Badge?
A film
badge is a thin plastic container which
opens at a hinge.
Inside there is a piece of film behind some windows (see
below).
People who work with radioactivity (or X-rays) wear
a
film badge to monitor their exposure.
Radiation will make
photographic film darken
in the same way
that exposure
to light and
X-rays do. The greater
the amount of
radiation
that the film is exposed to, the darker the film
becomes.
What is the Meaning in Physics
of the word Window?
People who do physics use the
word "window"
for any
substance which allows a wave or
particle
to pass
through it. The glass windows in
your
house allow light to
pass through them. An aluminium
window would allow gamma rays to
pass through.
A film badge
has spaces in the plastic in front of the film
containing thin windows of
paper, aluminium and lead.
Below is a picture of a film badge.
When the film is developed it gives an indication of the exposure
to
the type and amount of radiation the film
badge has received.
You can work out what type of
radioactivity will reach the film
behind the different materials
by looking at the penetrating ability.
The film
badge is a cheap and convenient method of
monitoring exposure to radiation. A Geiger-Müller
tube is a more precise method of measuring
radiation.
Links
Radioactivity
Revision Questions
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