11.2. Radioactive Decay http://www.ck12.org
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URL: http://www.ck12.org/flx/render/embeddedobject/5016- Alpha particles can travel only a few centimeters through air. They cannot pass through a sheet of paper or
thin layer of clothing. They may burn the skin but cannot penetrate tissues beneath the skin. - Beta particles can travel up to a meter through air. They can pass through paper and cloth but not through a
sheet of aluminum. They can penetrate and damage tissues beneath the skin. - Gamma rays can travel thousands of meters through air. They can pass through a sheet of aluminum as well as
paper and cloth. They can be stopped only by several centimeters of lead or several meters of concrete. They
can penetrate and damage organs deep inside the body.
FIGURE 11.8
It’s easy to stop alpha particles and even
beta particles. However, it’s very difficult
to stop gamma rays.Rate of Radioactive Decay
A radioactive isotope decays at a certain constant rate. The rate is measured in a unit called thehalf-life. This is
the length of time it takes for half of a given amount of the isotope to decay. The concept of half-life is illustrated
inFigure11.9 for the beta decay of phosphorus-32 to sulfur-32. The half-life of this radioisotope is 14 days. After