median
don steward
mathematics teaching 10 ~ 16

## Tuesday, 24 March 2009

### half life

the half life is the amount of time it takes for half of the nuclei in some radioactive matter to decay

Radium has a half life of around 1600 (various values are quoted, from 1590 to 1620) years
• how long before Radium reduces to 25% of its nuclei?

(a general decay graph from OpenStax college)

Protactinium 234 (a grandchild of Uranium) has a half life of 77 seconds
produce a table showing the % of nuclei present every 10 minutes

a YouTube clip shows an experiment monitoring this decay:
every 10 seconds the count pauses
then there is a 2.5 second delay
until the next 10 second count starts
and so on

the clip states that the background radiation count (to be subtracted) is 6 counts per 10 seconds

• students can plot an accurate graph of this experimental decay

Carbon 14 (used to carbon date ancient artifacts) has a half life of approximately 5700 years

(BBC Bitesize)

• what equation models the link between % and time?