4.4.2.3 - Half lives and the random nature of radioactive decay

Is radioactive decay random or not random?

Random process

What is meant by the ‘half-life’ of a radioactive isotope?

The half life of a radioactive isotope is the time taken for the number of radioactive nuclei in the sample to halve

Or it’s the time take for the count rate (activity) from a sample containing the isotope to fall to half it’s initial level ( so the amount to radiation emitted)

Do older or new sources emit more radiation?

Newer sources emit more radiation

Older sources emit less as the radioactivity of a source decreases over time

Why do we use half lives as a measure?

Half lives are used as activity never reaches zero

Describe a short half-live?

Means that the activity of the source falls quickly

This is as the nuclei are very unstable and decay rapidly

Why are short half lives dangerous?

Can be dangerous - due to the high amount of radiation they emit initially (at the start)

But they quickly become safe

Describe long half-lives.

• means activity falls more slowly

• Due to most of the nuclei no decaying for a long time

Why are long half lives dangerous?

Can be dangerous as nearby areas are exposed to radiation for (millions( of years