12. Alpha and Beta tracks

When there was no ionising radiation present Wilson found that the clouds showed a uniform distribution of droplets.

When the chamber was ionised with alpha-particles clear, straight tracks were emitted from the radium source. Wilson said his photographs gave 'a poor idea of the really beautiful appearance of these clouds'..

Beta-particles produced 'two or three absolutely straight thread-like lines' from the direction of an impure radium salt source. The tracks produced by beta-particles were less clear than those produced by alpha-particles. Less energetic particles would spiral in the earth's field.

We now know that beta-particles are electrons and alpha-particles are atomic nuclei of the element helium. Beta-particles are negatively charged while alpha-particles have a positive charge of twice the magnitude. Alpha-particles are more ionising than beta-particles.

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