Quiz-8 Solns

Quiz-8 Solns - Quiz #8: Nuclear Physics April 23, 2007...

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Unformatted text preview: Quiz #8: Nuclear Physics April 23, 2007 Complete both of the following problems. Show all of your work for full credit. Problem 1 A researcher has found 1g of U (Uranium) in a rock which age is estimated as 1 billion years. Calculate the initial mass of U assuming that it has been formed 1 billion years ago. 238 U is the most common U isotope having a half-life of 4.468109 years. Since N=N0exp(-t/), the mass of the radioactive sample decays the same way: m=m0exp(-t/) where t = 1109 years, because the mass is proportional to the number of nuclei in the sample. 238 Solutions = t1/ 2 4.468 109 yr = = 6.447 109 yr ln 2 0.693 1 109 yr t = 1.168 g . m0 = m exp = 1 g exp 6.447 109 yr Problem 2 Write down the decay equation for radioactive lead this reaction. 204 Pb and find the energy released in - decay : Q= M 204 82 4 Pb 200 Hg + 2 80 200 80 {[ ( 204 82 Pb - M )] [ ( ) ( Hg + M ) ( 4 2 He c 2 = )]} = {203.973029u - 199.968309u - 4.002603u}c 2 = 2.117 10 -3 u c 2 = 2.117 10 -3 931.49 MeV / c 2 c 2 = 1.972 MeV { } {( )} ...
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This homework help was uploaded on 04/22/2008 for the course PHYS 320 taught by Professor Baski during the Spring '04 term at VCU.

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