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.

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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.

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Figure 21.9 A Geiger counter.
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scintillation counter

• A device that detects nuclear radiation from
  flashes of light generated in a material by the
  radiation.
• Detector counts flashes of light.

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Figure 21.10 A diagram of how a scintillation
probe works.
Return to slide 50
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Half-life

• 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

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19.4 Dating by Radioactivity

• Radiocarbon dating or carbon-14 dating
• Based on the radio activity of carbon-14 which
  decays by beta particles.