24.1. Nuclear Radiation http://www.ck12.org
Measurement of exposure to radioactivity is important for anyone who deals with radioactive materials on a regular
basis. Perhaps the simplest device is a personal dosimeter, which is a film badge that will fog up when exposed to
radiation. The amount of fogging is proportional to the amount of radiation present.
FIGURE 24.5
These devices are not very sensitive to low levels of radiation, but more sensitive devices are also available that
reliably measure the frequency of radioactive events. One such device is the Geiger counter. AGeiger counter
is a tube filled with an inert gas that will conduct electricity when exposed to charged radiation, such as alpha or
beta particles. When a charged particle enters the tube, it changes the electrical potential between the anode and
the cathode, and this change in potential is registered by an electrical circuit as a single radioactive event. Geiger
counters are fairly inexpensive and reliable, so they are useful in a wide range of applications. More complicated
types of counters are also available, but are generally used only in sophisticated experiments.
Lesson Summary
- Radioactivity involves the release of particles and/or energy from the nucleus of an atom.
- Alpha emissions consist of the ejection of an alpha particle (a helium-4 nucleus) from a radioactive nucleus.
- Beta emission involves the conversion of a neutron into a proton (which remains in the nucleus) and an electron
(beta particle) that is ejected from the nucleus. - Positron emission involves the conversion of a proton into a neutron (which remains in the nucleus) and a
positron, which is ejected from the nucleus. - Gamma emission is the release of energy in the form of high energy electromagnetic waves.
- Radiation dosage can be measured in several ways, including personal dosimeters and Geiger counters.