7.10 to 7.12 starter · Smoke detectors use 241Am to emit alpha particles which pass through a small air gap before being detected. If smoke particles are present they interrupt the beam of alpha particles and this triggers the alarm to go off
· Tomorrow, will the 241Am still be as radioactive?
· Next year, will the 241Am still be as radioactive?
· In a thousand years, will the 241Am still be as radioactive? Answers
· To answer the questions, we need to know the half life of Americium-241 which is 432 years
· Tomorrow and even next year its activity will hardly have changed at all (sensible for a smoke detector - you don't want it to suddenly stop working!)
· In a thousand years its activity will have dropped to about a quarter 7.10 to 7.12 · 7.10 understand that the activity of a radioactive source decreases over a period of time and is measured in becquerels
· 7.11 recall the term ‘half-life’ and understand that it is different for different radioactive isotopes
· 7.12 use the concept of half-life to carry out simple calculations on activity Half-life of Different Isotopes
· http://youtu.be/S-goxH05LbY PhET animation - alpha decay Website http://phet.colorado.edu/en/simulation/alpha-decay
PhET animation - beta decay Website http://phet.colorado.edu/en/simulation/beta-decay 
· Tomorrow, will the 241Am still be as radioactive?
· Next year, will the 241Am still be as radioactive?
· In a thousand years, will the 241Am still be as radioactive? Answers
· To answer the questions, we need to know the half life of Americium-241 which is 432 years
· Tomorrow and even next year its activity will hardly have changed at all (sensible for a smoke detector - you don't want it to suddenly stop working!)
· In a thousand years its activity will have dropped to about a quarter 7.10 to 7.12 · 7.10 understand that the activity of a radioactive source decreases over a period of time and is measured in becquerels
· 7.11 recall the term ‘half-life’ and understand that it is different for different radioactive isotopes
· 7.12 use the concept of half-life to carry out simple calculations on activity Half-life of Different Isotopes
· http://youtu.be/S-goxH05LbY PhET animation - alpha decay Website http://phet.colorado.edu/en/simulation/alpha-decay
PhET animation - beta decay Website http://phet.colorado.edu/en/simulation/beta-decay
