Measurements indicate that a fossilized skull you unearthed has a carbon-14: carbon-12 ratio about 1/16th that of the skulls of present-day animals. What is the approximate age of the fossil? (The half-life of carbon-14 is 5,730 years.)

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Hi everyone welcome back. Here's our next problem in radiocarbon dating. Carbon isotopes are used to calculate the age of the fossil as the sample ages. The amount of blank never changes while the amount of blank is constantly changing. So let's briefly look over our answer choices and there's one we can eliminate right away because choice d says oxygen 12, oxygen 14. But we says right here in our problem that they use carbon isotopes. So we're definitely not gonna be using oxygen isotopes. So now we've got our choices of carbon 1213 and 14. When we look at our other entry choices. So let's recall from our content video how carbon dating works. Put up this little image here, we know that when an organism dies it stops replenishing the carbon supply it gets either from carbon dioxide in the air if you're a plant or from ingesting carbon containing materials. So at that point No more carbon comes in and the organism at the point of death has a certain ratio of carbon 12 to carbon 14. Those are the two isotopes. We look at carbon 12 is a stable isotope of carbon. And so it remains the same. It does not change. It does not decay. However, carbon 14 is radioactive. So over time the carbon 14 will be decreasing. It will be the king. And so you will see less and less carbon 14 over time as a fossil ages. So compared to the point of death at the point of death there will be a certain ratio of carbon 12 to carbon 14 in the organism. When we look at a fossil, we'll see the older it is, the higher that ratio will be because the amount of carbon 12 which remains the same, will be stable compared to the decreasing amount, the smaller and smaller amount of carbon 14. So we have carbon 12 Never changing and carbon 14 constantly changing. So let's look at our answer choices and we see that choice a. Has carbon 12 Followed by carbon 14 and therefore is our answer. When we look at our other answer choices. Choice B has them in the wrong order. So that's not our answer. And choice c. Has carbon 13 in there, which is not one of the isotopes we look at. So that's not a correct answer. So again, in radiocarbon dating, carbon isotopes are used to calculate the age of the fossil as a sample age is the amount of choice a carbon 12 never changes. While the amount of carbon 14 is constantly changing. See you on next video

Measurements indicate that a fossilized skull you unearthed has a carbon-14: carbon-12 ratio about 1/16th that of the skulls of present-day animals. What is the approximate age of the fossil? (The half-life of carbon-14 is 5,730 years.)

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Key Concepts

Carbon-14 Dating

Half-Life

Exponential Decay