Radioactivity and Nuclear Reactions

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Slide 48

Radioactive Dating

Scientists often want to know the ages of rocks & fossils using radioactive isotopes & their half-lives.

Slide 49

Radioactive Dating

Scientists often want to know the ages of rocks & fossils using radioactive isotopes & their half-lives.

The amount of the radioactive isotope in object is measured, then the amount of the daughter nuclei is measured. With these the number of half-lives or age of the object can be calculated.

Slide 50

How is carbon used to date objects?

Carbon-14, with a half-life of 5,730 years is often used to estimate the age of plant & animal remains.

Slide 51

How is carbon used to date objects?

Carbon-14, with a half-life of 5,730 years is often used to estimate the age of plant & animal remains.

CO2 which plants use in photosynthesis contains C-14 which stays in the same ratio while alive.

Slide 52

How is carbon used to date objects?

Carbon-14, with a half-life of 5,730 years is often used to estimate the age of plant & animal remains.

CO2 which plants use in photosynthesis contains C-14 which stays in the same ratio while alive.

Once it dies, C-14 decreases as the C-12 increases over time. The ratio estimates ages up to 50,000 years.

Slide 53

How is uranium used to date objects?

Some rocks can be dated using the amount of radioactive uranium isotopes that have decayed into lead.

Slide 54

How is uranium used to date objects?

Some rocks can be dated using the amount of radioactive uranium isotopes that have decayed into lead.

The ratio of the amounts of U isotopes & and their daughter nuclei are compared to estimate the age of the rock.

Slide 55

Detecting Radioactivity

What You’ll Learn

How cloud and bubble chambers are used to detect radioactivity

How an electroscope is used to detect radiation

How a Geiger counter measures radiation

Slide 56

Radiation Detectors

Special instruments detect the electric charge of the ions formed by the radioactive particles as they pass through matter.

Slide 57