Discussion topic:
Describe the differences between half-life and mean or average life. Which is longer? Find some examples of how each are used when discussing radioactivity.
Discussion post:
Half-life and average life are two values of importance in radiation dosimetry but they are important in other studies as well. According to Kahn and Gibbons1 half-life is a function of the amount of time it takes for a radioactive sample to decay by half.1 A half-life measurement does not consider individual atoms rather it measures the given sample as a whole. Average life is a measurement that considers all radioactive atoms within a sample divided by the number of atoms that make up the sample.1 The equation Ta = 1.44 T1/2 demonstrates that average life measurement is always greater than a half-life measurement because average life considers the total of all nuclei involved.1
Half-life and mean life are values also important in the process of carbon dating of fossils. The carbon dating process measures the amount of 14C in a fossil. The amount of 14C is useful because it has been determined that in living organisms the amount of 12C is proportional to the amount of 14C and once an organism dies 12C is no longer produced. Thus by measuring the amount of 14C in a fossil compared to 12C we can determine how long the fossil has been nonliving. The decay constant for 14C is 5700 years and by measuring the amount of 14C present in a given fossil and accounting the half-life of 14C we can determine a fossil’s age using the principals of half-life and average life.2
References
1.Khan FM, Gibbons JP. The Physics of Radiation Therapy. 5th Philadelphia, PA: Lippincott Williams and Wilkins. 2014.
2.The Biology Project University of Arizona. Carbon Dating to determine the age of fossil remains. Biology.arizona.edu. http://www.biology.arizona.edu/biomath/tutorials/applications/carbon.html. Accessed on September 6, 2016.
Describe the differences between half-life and mean or average life. Which is longer? Find some examples of how each are used when discussing radioactivity.
Discussion post:
Half-life and average life are two values of importance in radiation dosimetry but they are important in other studies as well. According to Kahn and Gibbons1 half-life is a function of the amount of time it takes for a radioactive sample to decay by half.1 A half-life measurement does not consider individual atoms rather it measures the given sample as a whole. Average life is a measurement that considers all radioactive atoms within a sample divided by the number of atoms that make up the sample.1 The equation Ta = 1.44 T1/2 demonstrates that average life measurement is always greater than a half-life measurement because average life considers the total of all nuclei involved.1
Half-life and mean life are values also important in the process of carbon dating of fossils. The carbon dating process measures the amount of 14C in a fossil. The amount of 14C is useful because it has been determined that in living organisms the amount of 12C is proportional to the amount of 14C and once an organism dies 12C is no longer produced. Thus by measuring the amount of 14C in a fossil compared to 12C we can determine how long the fossil has been nonliving. The decay constant for 14C is 5700 years and by measuring the amount of 14C present in a given fossil and accounting the half-life of 14C we can determine a fossil’s age using the principals of half-life and average life.2
References
1.Khan FM, Gibbons JP. The Physics of Radiation Therapy. 5th Philadelphia, PA: Lippincott Williams and Wilkins. 2014.
2.The Biology Project University of Arizona. Carbon Dating to determine the age of fossil remains. Biology.arizona.edu. http://www.biology.arizona.edu/biomath/tutorials/applications/carbon.html. Accessed on September 6, 2016.