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InterviewSolution
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The normal activity of living carbon-containing matter is found to be about 15 decays per minute for every gram of carbon. This activity arises from the small proportion of radioactive " "_(6)^(14)C present with the stable carbon isotope " "_(6)^(12)C. When the organism is dead, its interaction with the atmosphere (which maintains the above equilibrium activity) ceases and its activity begins to drop. From the known half-life (5730 years) of " "_(6)^(14)C, and the measured activity, the age of the specimen can be approximately estimated. This is the principle of" "_(6)^(14)C dating used in archaeology. Suppose a specimen from Mohenjodaro gives an activity of 9 decays per minute per gram of carbon. Estimate the approximate age of the Indus-Valley civilisation. |
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Answer» Solution :GIVEN, NORMAL activity `R_(0)`=15 decays per minute, Present activity R =9 decays per minute, and Half-life `T_(1/2)` = 5730 YEARS Since `R=R_(0)e^(-lamda t) IMPLIES R_(0)/R=e^(lamdat) or t=1/(lamda)ln R_(0)/R=1/(lamda)ln(15/9)` But `lambda=0.693/T_(1/2) = 0.693/5730 Year^(-1)` `therefore t= 5730/0.693 In(15/9)`year =4225 years |
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