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19.3 Detection of radioactivity

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19.3 Detection of radioactivity
Two types of devices, Geiger
counter and scintillation counters,
are used to count particles emitted
from radioactive nuclei.
Geiger counter
A kind of ionization counter used to
count particles emitted by radioactive
nuclei, consists of a metal tube filled
with gas, such as argon.
Radioactive decay produces ion when
moving through matter such as argon.
This fast moving particle knocks off
electron from argon.
Speaker gives “click” sound for each
particle.
Figure 21.9: A Geiger counter.
scintillation counter
A device that detects nuclear radiation
from flashes of light generated in a
material by the radiation.
Detector counts flashes of light.
Figure 21.10: A diagram of how a scintillation probe works.
Return to slide 50
Half-life
п‚Ў
п‚Ў
п‚Ў
п‚Ў
п‚Ў
п‚Ў
Time required for half of the original
sample of nuclei to decay.
1000 nuclei, half life = 500 nuclei
The shorter the half life, the more
likely to decay
Pa half life = 1.2 minutes
U half life – 4.5 billion years
Pa “hotter”, shows more reactivity
19.4 Dating by Radioactivity
п‚Ў
п‚Ў
Radiocarbon dating or carbon-14
dating
Based on the radio activity of
carbon-14 which decays by beta
particles.
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