On the last day of recording the 2012 Christmas Lectures Dr Peter Wothers illustrates the properties of Air with a beautiful demo from his final Lecture.
The Cloud Chamber shows the natural radiation in the atmosphere. When the charged alpha particles and smaller beta particles fire through the alcohol-heavy atmosphere in the chamber they cause little droplets to form leaving cloud-like trails.
When Dr Wothers introduces a sample of the artificially-produced radioactive metal Americium into the chamber the alpha particles emitted (with their two protons and two neutrons) grab electrons and form Helium atoms.
Watch this experiment in the 2012 Christmas Lectures, The Modern Alchemist, on the Ri Channel:
http://bit.ly/VJM09x
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