Chapter 2
Types of Radiation and Their Properties
Radiation and radioactivity are physical phenomena that have been well-described
by science. An understanding of their physical properties and an appreciation of the
relevant science is essential if we are to understand how to evaluate the risks they
pose, the measurements we make, recommended safety measures, and so forth. For
this reason, we will start with a review of the fundamental science that underlies the
field of radiation safety and its applications. In addition, the reader should consider
that, in the midst of a radiological or nuclear emergency, it might not be necessary
to develop precise calculations—quick estimate is often good enough, with more
detailed calculations coming when the emergency phase is over. At times, a rough
answer that comes quickly can be more useful than a precise answer that arrives hours
or days later. Finally, please note that this is a quick review of the basic concepts and
is not intended to be comprehensive or in-depth; those interested in a more in-depth
understanding of the topic should consider an introductory textbook (e.g., [1, 2],
among others).
2.1 What Radiation and Radioactivity Are
Radiation, to a physicist, is nothing more—or less—than the emission of energy
by an object and the transmission of that energy to a different location. A toaster
does this; a toaster emits thermal radiation that is transferred to a piece of bread.
To most members of the general public, radiation is a dangerous and mysterious
phenomenon that glows, mutates, and kills. What the public thinks of as “radiation”
is more specifically referred to as “ionizing radiation”—radiation that carries with
it enough energy to strip an electron from an atom to create a pair of ions where
there had previously been an uncharged atom. It is this process of ionization that can
initiate the chain of events that can lead to health problems. The threshold energy
for causing an ionization is about 5 electron volts (eV); for photons this corresponds
© Springer Nature Switzerland AG 2021
P. A. Karam, Radiological and Nuclear Terrorism,
Advanced Sciences and Technologies for Security Applications,
https://doi.org/10.1007/978-3-030-69162-2_2
5
Types of Radiation and Their Properties
Radiation and radioactivity are physical phenomena that have been well-described
by science. An understanding of their physical properties and an appreciation of the
relevant science is essential if we are to understand how to evaluate the risks they
pose, the measurements we make, recommended safety measures, and so forth. For
this reason, we will start with a review of the fundamental science that underlies the
field of radiation safety and its applications. In addition, the reader should consider
that, in the midst of a radiological or nuclear emergency, it might not be necessary
to develop precise calculations—quick estimate is often good enough, with more
detailed calculations coming when the emergency phase is over. At times, a rough
answer that comes quickly can be more useful than a precise answer that arrives hours
or days later. Finally, please note that this is a quick review of the basic concepts and
is not intended to be comprehensive or in-depth; those interested in a more in-depth
understanding of the topic should consider an introductory textbook (e.g., [1, 2],
among others).
2.1 What Radiation and Radioactivity Are
Radiation, to a physicist, is nothing more—or less—than the emission of energy
by an object and the transmission of that energy to a different location. A toaster
does this; a toaster emits thermal radiation that is transferred to a piece of bread.
To most members of the general public, radiation is a dangerous and mysterious
phenomenon that glows, mutates, and kills. What the public thinks of as “radiation”
is more specifically referred to as “ionizing radiation”—radiation that carries with
it enough energy to strip an electron from an atom to create a pair of ions where
there had previously been an uncharged atom. It is this process of ionization that can
initiate the chain of events that can lead to health problems. The threshold energy
for causing an ionization is about 5 electron volts (eV); for photons this corresponds
© Springer Nature Switzerland AG 2021
P. A. Karam, Radiological and Nuclear Terrorism,
Advanced Sciences and Technologies for Security Applications,
https://doi.org/10.1007/978-3-030-69162-2_2
5