ABSTRACT
This chapter provides an introduction to units and quantities, and also provides brief descriptions of nuclear and atomic principles. It describes the development of various atomic models, the mechanisms and mathematics of radioactive decay, and the interaction of radiation with matter. Physical quantities are organized in a system of dimensions, with each of the seven base quantities used in the System of Units (SI) having its own dimension. All other quantities are derived quantities: they can be written in terms of the base quantities, and their dimensions are products of powers of the dimensions of the base quantities. The protection quantities are intended to relate overall risk and are developed using humanoid phantoms meant to represent reference persons. In order to be meaningful, the value of a quantity must be expressed using both a value and a unit. The chapter concludes by covering the principles of radiation dosimetry, including some of the various quantities that may be of interest.
