Half-Life

Radioactivity is a ________ process

Random

Radioactive substances give out ______ from the ____ of their atoms.

1. Radiation

2. nuclei

How is radiation measured?

With a Geiger-Muller tube and counter, which records the count-rate (number of radiation counts reaching it per second)

What is half- life?

the time it takes for the number of radioactive nuclei in an isotope to halve.

What is half-life used for?

• it can be used to make predictions about radioactive source.

• Find the rate at which sources decays (its activity, meaured in becquerels, Bq)

A short-half life means…?

The activity falls quickly, because the nuclei are very unstable and rapidly decay. This can be harmful at the start because it releases a lot of energy in a short time, but it takes less time to become stable/safe.

A long half-life means…?

The activity slowly falls because most of the nuclei is stable. This can be harmful because it is releasing little radiation to the surroundings for a long period of time.

How to calculate half-life

1. Find the activity of each half-life (initial and final). you can do that by diving the initial by 2 and halving the result.

2. Divide the final activity by the intial activity.

3. Times it by 100 to get a percentage.

Summary

The activity of a source will never reach zero. which is why we have to use half-life. if the activity is short it means the isotopes is highly unstable and its rapidly releasing radiation/decaying to become stable. They can be very harmful at the start since they are releasing lots of radiation rapidly but they will take less time to become safe.

The more unstable the isotope is, the shorter the activity will be. Opposite happens with long half-life, but they are more dangerous since they are releasing little energy for a very long time.