Pre-Class Warm-Up Exercise
Due by 6 AM on April 26, 2012

(Physics 204, Spring 2012)

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Reading: Chapter 20


1. The activity of 1 g of radium defines the Curie (Ci), and turns out to be 3.7 x 1010 disintegrations per second. Knowing that the activity is αN, where N is the number of atoms present, find the apparent decay rate α. You will need to know that natural radium is mostly the longest lived isotope, Ra226.



2. Use this decay rate α to find the corresponding radium half life T1/2.


3. The half life of Ra226 is actually 1622 years. Why is the answer to (2) above close to this but a bit shorter?


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