00:04
If we are told that a certain sequoia tree that was cut down in 1891 had 1 ,342 annual growth rings, how do we determine the difference in the c -14 to c -12 ratio in the oldest ring versus the younger string? so let's just try to write down the information available in this question.
00:37
Because the tree trunk contained 1 ,342 growth rings, it means the time difference that we are concerned about, or here, in this case, t, is equal to 1342 years.
00:54
T half is a constant for a particular radioactive isotope and for the c14 radio nucleides, it's 5 ,730 years.
01:15
So let's use this information to calculate the difference in the c -14 to c -12 ratio.
01:24
So we also have this other equation that we will be using in this case.
01:29
We know that the fraction of radioactive isotopes present at time t, which is equal to nt over n o, is equal to 0 .5 times, i'm sorry, 05 to the power t divided by t half.
01:56
Let's substitute for these values.
02:00
So we know that t is equal to 1 ,342...