Quiz 5 Solns

Quiz 5 Solns - Phys320 Spring 2004 (Baski) Quiz #6: Nuclear...

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Phys320 – Spring 2004 (Baski) Quiz #6: Nuclear Physics April 21, 2004 Name: ___SOLUTIONS _____ Complete both of the following problems. Show all of your work for full credit. Problem 1: Radioactivity The counting rate from a radioactive source is initially 4 million decays per second, and it decreases to 500,000 s –1 after 6 seconds. Find the τ and half-life of this source in seconds. Also, find the counting rate after 20 seconds has elapsed. Solving for τ in the decay equation R = R o e – t/ τ gives: ( 29 ( 29 1/2 6 5 6 11 6s 2.885 s an d ln 2 (2.885)(0.693 ) 2.0s 4 10 ln ln 5 10 ex p ( 4 1 0 )ex p 20 s 2.885 s 3,90 3s o o t t tt R R R R ts t -- = = = = == 
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