02 February 2012
10:30
· 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
12 January 2012
10:24
· 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
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PhET animation - alpha decay
31 January 2012
13:34
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Website
http://phet.colorado.edu/en/simulation/alpha-decay
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PhET animation - beta decay
31 January 2012
13:34
>
Website
http://phet.colorado.edu/en/simulation/beta-decay
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