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Unformatted text preview: 514 Radioactivity Chap. 5 20. Charcoal found in a deep layer of sedimentin a caveis found to have an atomic 14Cj12Cratio only 30% that of a charcoal sample from a higher level with a known age of 1850y. What is the age of the deeperlayer? Solution: Let R denote the atomic ratio of 14Cto 12C.We assumethe same initial ratio was incorporated into both layers when they were formed, i.e., Rd(O)= Rh(O). Then the present ratio in the deeper layer to that in the higher layer is 1 td =th ~ln [~ ~(td) (P5.8) For 14C, ). = In2/Tl/2 = 1.21 x 104 yl, and for the given information that R(td)/R(th) = 0.30 and th = 1850y, Eq. (P5.8) gives the desired age as
td = 1850 41n(0.30) 1.21 x 10 1 = 11,800 y. July 24, 2002 ...
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This note was uploaded on 02/01/2010 for the course ECE 4130 taught by Professor Cady during the Spring '06 term at Cornell University (Engineering School).
 Spring '06
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