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THE EXPONENTIAL DECAY LAW:
In 1902, while studying the radioactivity of thorium, Rutherford and the
English chemist Frederick Soddy discovered that radioactivity was linked
to changes within the atom that altered thorium into a different element.
They found that thorium continually produces a chemically different substance
that is intensely radioactive. The radioactivity eventually makes the
new element cease to exist.
Based on this experiment, Rutherford and Soddy formulated
the exponential decay law. This law states that
a fixed fraction of the element will decay in each unit of time.
They showed that half of the thorium product decays in four days, half
the remaining portion in the next four days, and so on.
How To Use: Here we study radioactive decay. Shown (red
dots) is a large number of identical atomic nuclei, each obeying the same
decay law. Now select the half life time of the nuclei with the slider,
press the START button, and watch them decay away as a function of time
(displayed in the upper right corner). Shown also is a histogram (in green)
of the number of nuclei remaining at a given time.
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