Here we will explore half-life and activity, the quantitative terms for lifetime and rate of decay. The answer can be found by examining Figure 22.27, which shows how the number of radioactive nuclei in a sample decreases with time.The time in which half of the original number of nuclei decay is defined as the .
The maximum neutrino flux in the sample in their experiments was several times greater than the flux of neutrinos from the sun.The researchers followed the gamma-ray emission rate of each source for several weeks and found no difference between the decay rate of the spheres and the corresponding foils.Even if it happens to survive hundreds of half-lives, it still has a 50 percent chance of surviving through one more.Therefore, the decay of a nucleus is like random coin flipping.Recent puzzling observations of tiny variations in nuclear decay rates have led some to question the science of using decay rates to determine the relative ages of rocks and organic materials.
Scientists from the National Institute of Standards and Technology (NIST), working with researchers from Purdue University, the University of Tennessee, Oak Ridge National Laboratory and Wabash College, tested the hypothesis that solar radiation might affect the rate at which radioactive elements decay and found no detectable effect.
Carbon-14 has an abundance of 1.3 parts per trillion of normal carbon, so if you know the number of carbon nuclei in an object (perhaps determined by mass and Avogadro’s number), you can multiply that number by in an artifact, such as mummy wrappings, with the normal abundance in living tissue, it is possible to determine the artifact’s age (or time since death).
Carbon-14 dating can be used for biological tissues as old as 50 or 60 thousand years, but is most accurate for younger samples, since the abundance of nuclei in them is greater.
Provided the number of nuclei is reasonably large, half of the original nuclei should decay during one half-life period.
), the number decreases to half of its original value.
National Institute of Standards and Technology (NIST).