Half-life | Physics | Khan Academy

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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[khanacademy]

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[subjectnether]

"Gordon doesnt need to hear all this, he's a highly trained professional."

[MightyMakin]

Gordon doesn’t need to hear all of this, he’s a highly trained professional

[МиланЖивковић-къ]

Clicked cause of the game, stayed out of curiosity. Wasn't dissapointed.

[Mahesh_Shenoy]

‘Please, leave me alone until after the experiment!’

[tomspoors]

An excellent analogy with the random coin toss. Especially the fact that we cannot know which individual will 'leave' the game, just that 'on average' half will.

[AnneOfCottage]

This was hella briliant My teachers complain all the time taht there isnt enough time in a single period to go through these topics but u just did it so well, precise and elegantly

[SamraAli-je]

I've never seen someone teach so well, he should def upload more physics related videos!

[ipalomino]

Nice video, thanks.

But how do we know that the half-live of C14 is 5730 years? Radioactivity was discovered on the 19th century, right?

[Manigo]

But how do we know that uranium has a half-life of 4.5B years? It is not like we can sit around and wait to see how long it takes for half of it to disappear. Even with a large amount, and waiting for something like 100 years, would it even be noticable?

[mannatbhatia]

Khan Academy never fails to explain things perfectly!

[manoprakash]

That was awesome. Keep up the good work.

[FOOTBALL-hwqy]

Why half life is 5730? Why not something else? Cz the atmosphere around the globe is not the same!

[manjugagare]

Wouldn't this apply that all carbon atoms should decay into nitrogen