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igcse physics notesprinted 118 · PDF 118
124 pagesrevision 46936
printed 118 · PDF 118
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118
Half-lives of isotopes and their uses
The half-life of an isotope is defined as the average time taken for half the
atoms in a sample of radioactive material to decay.
These isotopes are used for different purposes, which depends on their
half-lives and the type of radiation emitted.
In smoke detectors, an element Americium is used, which has a long half
life of about 430 years. This makes it so that the count rate of the source
does not change dramatically in a long time. When smoke covers the
source, however, the count rate will drop dramatically and the fire alarm will
sound.