hello mr. gazda here today we're going to do
radioactive decay carbon 14 carbon dating this is going to be the example we're going to
use though it applies for all of radioactive dating
watch this, so a few things carbon-14 is a type of carbon and occurs naturally and
let's say for instance trees or any natural thing that has carbon in it and the one thing
that's unique about this this unstable isotopes of carbon 14 will decay
naturally become and turn into nitrogen-14 ok this is called the parent
this is called the daughter will naturally become nitrogen14 and the
time it takes for it to happen
is very set it doesn't change for carbon 14 the half life
is the word we use for is 5,700 years
half-life I'm going to describe what half life is and how that works
right now i'm going to use blue paper so in this case what i'm going to do is
I'm gonna say the blue paper represents carbon-14 so this is right at the - I'm going to write this in
the blue is carbon 14 in our example and then the white
you'll see in a second the white is nitrogen 14
ok so here we go so you start out and i'm going to say then 0 years ago when
that tree is growing what you have is all carbon 14 no nitrogen 14 so i will
put down you know 0 years have gone by and 0 half lives have gone by
ok after one half-life has gone by , what happens is half of the carbon-14 the blue will decay and
become nitrogen-14 and it will look like that
ok so that's one half life has gone by so that would be 5,700
years of time passed and one half life
ok another half life goes by so half of the carbon-14 the blue you have here
will become nitrogen-14 that will stay nitrogen-14 forever
it's stable so it will look like that
and now we're talking another 5,700 years
so this is a total time here that we are representing is eleven thousand four
hundred years and then that's two half-lives haved passed
ok let's do a third I hope you can see this pattern here
ok half and then half of this so after the third half life has past ok
half of this decays to white it looks like that so this is now
three
past lives have passed and in this case 3 half life times your
half-life of that is going to be I think it is seventeen thousand one hundred
years of time
all right want to do another one to one more half life
we will another one will look like this OK get half of that looks
like this and then the last four half lives five half lives
come by and that will continue right but and the that rate is constant 5,700
years and that will continue on until you will never get rid of the car before
you always be somewhat but we'll get to a point down the road I think they're
usually like fifty sixty thousand years is kind of - all and the other than that
you can't use carbon 14 today because there's just so little of it left is
very hard to measure so over this helps is a difficult concept for students
often to grasp but i hope this helps
mr. gasta thanks for watching
yeah