Half-life | Physics | Khan Academy

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Half-life is the time required for half of a radioactive sample to decay. Half-life cannot be changed—nuclei cannot be forced to decay faster or slower. Additionally, we cannot predict when an individual nucleus will decay. However, when analyzing a large sample containing many nuclei, half-life allows us to predict how much of the sample will remain after a given amount of time. This is useful for radiometric dating.

Sections:
00:00 - Intro
00:34 - What is half-life?
03:26 - Coin toss analogy
05:50 - Radioactive decay is spontaneous
06:37 - Why care about half-life?
07:20 - Decay graph
08:30 - Radiometric dating

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