1. 19.3 Detection of radioactivity
Two types of devices, Geiger counter and scintillation counters, are used to count particles emitted from radioactive nuclei.

2. 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.

3. Figure 21.9: A Geiger counter.

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

5. Figure 21.10: A diagram of how a scintillation probe works.
Return to slide 50

6. 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

7. 19.4 Dating by Radioactivity
Radiocarbon dating or carbon-14 dating
Based on the radio activity of carbon-14 which decays by beta particles.