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Detecting Radioactivity - Geiger-Müller tube.
A Geiger-Müller
tube detects the ions which are formed by radioactivity.
The tube is filled with argon gas
and has a very thin piece of
mica at the end.
It is called a mica window,
and it lets all types of radioactivity penetrate through it, even a-particles.
When an electron is knocked
off an argon atom, a
positive ion is formed.
The ion is attracted to the
negative inside of the tube.
When the ion collides with the
tube it
collects an electron and becomes an argon atom again.
The electron which was knocked
off is attracted to the
central positive wire.
When the electron collides with the positive
wire,
the tiny amount of electricity causes a click
from the loudspeaker of the
counter.
The counter has a digital display of
the number of clicks per second.
This is the same as the number of
radioactive waves or particles
which have entered the tube in one
second.
Radioactivity is measured in
Becquerels, symbol Bq.
1 Bq = 1 decay per second.
The Geiger-Müller
tube and the counter together
are often called a Geiger counter.
The count rate (reading)
obtained from a Geiger counter
depends on the distance of the
tube from the radioactive source.
The closer the tube is to the source,
the more radioactivity will
enter it and the higher the reading
will be.
The reading is also affected by the background count.
Headings Radioactivity Search
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Copyright © 2008 Dr. Colin France. All Rights Reserved.