11.1. Radioactivity http://www.ck12.org
FIGURE 11.3
This sign is used to warn people of dan-
gerous radiation.Detecting Radiation
One reason radiation is dangerous is that it can’t be detected with the senses. You normally can’t see it, smell it, hear
it, or feel it. Fortunately, there are devices such as Geiger counters that can detect radiation. A Geiger counter, like
the one inFigure11.4, has a tube that contains atoms of a gas. If radiation enters the tube, it turns gas atoms to ions
that carry electric current. The current causes the Geiger counter to click. The faster the clicks occur, the higher the
level of radiation. You can see a video about the Geiger counter and how it was invented at the URL below.
FIGURE 11.4
A Geiger counter detects radiation.Using Radiation
Despite its dangers, radioactivity has several uses. It can be used to determine the ages of ancient rocks and fossils.
This use of radioactivity is explained in this chapter’s "Radioactive Decay" lesson. Radioactivity can also be used
as a source of power to generate electricity. This use of radioactivity is covered later on in this chapter in the lesson
"Nuclear Energy." Radioactivity can even be used to diagnose and treat diseases, including cancer. Cancer cells grow
rapidly and take up a lot of glucose for energy. Glucose containing radioactive elements can be given to patients.
Cancer cells will take up more of the glucose than normal cells do and give off radiation. The radiation can be
detected with special machines (seeFigure11.5). Radioactive elements taken up by cancer cells may also be used
to kill the cells and treat the disease. You can learn more about medical uses of radiation at the URL below.