Today’s lesson Use the term half-life in simple calculations, including the use of information in tables or decay curves. Give and explain examples of practical applications of isotopes.

Nihalanitis

½ - life This is the time it takes half the nuclei to decay Number of nuclei undecayed A graph of the count rate against time will be the same shape time half-life (t½)

½ - life This is the time it takes half the nuclei to decay Number of nuclei undecayed A graph of the count rate against time will be the same shape time half-life (t½)

Different ½ - lives Different isotopes have different half-lives The ½-life could be a few milliseconds or 5000 million years! Number of nuclei undecayed time half-life (t½)

Example

Example A sample of a radioactive isotope of half life 2 hours has a count rate of 30 000 counts per second. What will the count rate be after 8 hours?

Summary of so far http://www.youtube.com/watch?v=PY0xvZaZsh4

Uses of radioactive isotopes

NOT nuclear power!

Subtitles On a double page can you write and underline the following subtitles (there are 6 of them) Tracers Killing microbes/sterilisation Thickness control Smoke detection Checking welds Dating

Used as Tracers

Used as Tracers

Used as Tracers

Killing microbes

Thickness control

Thickness control

Smoke detection

Checking welds

Carbon dating

Summary sheet http://www.youtube.com/watch?v=NzDLUALfqRQ

Reading – Pages 264-265

Can you use these pages to MAKE NOTES on the uses of radioactivity? Reading – Pages 264-265 Can you use these pages to MAKE NOTES on the uses of radioactivity?

“Can you………?”

Test! Tuesday 19th March (11B) Wednesday 20th March (11A)

Can you answer the questions on pages 261 and 265?