2010 PHYSICS 002C Lecture 28

2010 PHYSICS 002C Lecture 28 - PHYSICS 002C Format of the...

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PHYSICS 002C Lecture 28 June 4, 2010 Format of the final exam. Scrap paper and a Scantron F289-PAL-L will be provided. Bring a #2 pencil to mark it with. The exam, requiring a general understanding of the course, will be composed of 50 simple questions based on the 54 Problems in these lecture notes, problems which closely mirrored the home work. Seating will be assigned. Exams will be handed out at your seats upon verification of your identity. Simple calculators are permitted. Richard A. Muller, inventor of accelerator mass spectroscopy radiocarbon dating. Science 196 , pages 489-494, 1977 Chap. 30.4 Radiocarbon dating. C-14 isproduced in the upper atmosphere by (n,p) reactions on N-14, yielding a steady state concentration of radioactive C-14 equal to 12.5 decays per minute per gram of carbon. In 1949 W. F. Libby [ Science 109 , 227 (1949)] [1960 Nobel Prize in Chemistry] proposed using C-14 to determine the age of once living materials that have incorporated C from atmospheric CO 2 via photosynthesis. Accelerator mass spectroscopic radiocarbon dating allows one to detect C- 14 without waiting for it to decay. The increase in sensitivity is roughly one million, the ratio of the 5,700 year half life to the few hours that one can count beta particles before becoming swamped by background noise. This permits examining relatively small samples as is required for preserving precious objects, or for looking at small parts of something like individual tree rings. Two famous examples are as follows. Sample 1 gives radiocarbon dates for the Shroud of Turin measured by 3 laboratories. Sample 3 is from a 2,000 year old mummy. Nature 337 , 611 (1989). A 1x7 cm strip of linen was cut from the Shroud and divided into 3 parts to be analyzed in Arizona, Oxford, and Zurich ((A, O, and Z). The date of growth of the linen turns out to be about 1300 AD, very close to the date this object first appears in the available records. 1
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B.C. Science 312 , 548 (2006). Walter L. Friedrich, 1 * Bernd Kromer, Michael Friedrich, Jan Heinemeier, Tom Pfeiffer, Sahra Talamo 2 2,3 4 1 2 Precise and direct dating of the Minoan eruption of Santorini (Thera) in Greece, a global Bronze Age time marker, has been made possible by the unique find of an olive tree, buried alive in life position by the tephra (pumice and ashes) on Santorini. Island of Santorini Landscape of spring time - Fresco from the Bronze Age, Akrotiri. The olive tree section with individually carbon-dated growth rings Problems: Contamination with old carbon from limestone, fossil fuels, and volcanic activity making dates look older. Possible neutron activation making samples look younger, even with negative ages! [Tom Phillips,
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2010 PHYSICS 002C Lecture 28 - PHYSICS 002C Format of the...

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