[1]The early dangers from use of X rays, due to incomplete understanding
and inadequate shielding, have now been eliminated.
[2]Gamma rays are high-energy electromagnetic radiation.
[3]Alpha particles are large positively charged particles, identical to
helium nuclei. For definitions of unfamiliar words see _Nuclear
Terms, A Brief Glossary_, a companion booklet in this series.
[4]For detailed descriptions of these waves and particles, see _Our
Atomic World_, a companion booklet in this series.
[5]An equivalent statement is that nuclei of isotopes have the same
number of protons but different numbers of neutrons.
[6]See Appendix for a description of types of radiation-detection
instruments.
[7]See _Radioisotopes and Life Processes_, another booklet in this
series, for a discussion of one area of biomedical research.
[8]A positron is an “antielectron”. It has the mass of an electron but a
positive charge.
[9]A collimator is a focusing device consisting of a series of slits
between blocks of shielding material. Consult the Appendix for
descriptions of other instruments mentioned here.
[10]The superscript m after this isotope indicates an excited state of
the atom.
[11]As radioactive nuclei disintegrate, they change to other radioactive
forms—their “daughter” products. Every radioisotope is thus part of
a chain or series of steps that ends with a stable form.
Technetium-99^{m} is a daughter product of molybdenum-99; it decays
by a process known as isomeric transition to a state of lower energy
and longer half-life.
[12]The curie is the basic unit of radiation intensity. One curie is
approximately the amount of radioactivity in 1 gram of radium.
[13]See Your Body and Radiation and The Genetic Effects of Radiation,
other booklets in this series, for detailed explanations of
radiation effects.
[14]The use of radium is not under AEC control.
[15]One family of measuring instruments is described in
_Whole Body Counters_,
another booklet in this series. These are large devices that make
use of scintillating crystals or liquids.