physics notes

Concept of Half-life

1. The reactivity or activity of a radioactive material is the rate of decay of the material.

2. The rate of decay is the same as the number of atoms which decay or are emmited every second.

3. The rate of decay of a radioactive materials depends on the number of atoms that have not yet undergone decay. Thus, the reactivity of a radioactive material will decrease with time.

4. The half-life of a radioactive element is the time taken for half the number of atoms in a sample of radioactive atoms to decay.

Decay curve.

1. The half-life of the same radioactive element is the same but the half-lives of different radioactive elements are different.

2. The value of half-life is not influenced by factors such as temperatures, pressure and etc.

Usage of Half-life

Half-life in Archeology

1. Carbon-14 has a half-life of 5600 years.

2. Humus, animals and plants absorb carbon-14 through carbon

as carbon-14.

3. Living animals and vegetable have a constant amount of Carbon-14 because the c-14 decayed will always replaced.

4. However or dead beings the amount of C-14 in it will decrease because new C-14 will not be absorbed causing its reactivity to decrease.

5. When an antique or human skill are found, their age can be determined by

· Measuring the reactivity of C-14 in it.