3.1 Introduction

The broad definition of Industrial Radiography is as follows:

"The use of radiant energy in the form of X-rays or gamma rays for
nondestructive examination of opaque objects, (e.g., ferrous and non-ferrous
parts) in order to produce a radiograph (i.e., a photographic record) on
radiographic films (densely, double coated). The "radiographic image" thus
produced is used to locate internal flaws in the object being tested."

The term "Industrial Radiography" continues to be preferred and widely accepted
by the professionals in the field. However it is important to note that the
term "Industrial Radiology" is internationally preferred and accepted as it
encompasses all newer radiographic techniques, neutron radiography and the
related scientific principles.

Industrial Radiography utilizes an X-Ray apparatus or the radioactive isotope
as the source of X-rays or y-rays. These rays have the ability to penetrate
matter. (Typical examples of matter are steel castings, human tissues, etc.).
While penetrating through matter, these rays are selectively absorbed. This is
dependent upon the matter's chemical composition, density, geometry of
construction and thickness. Since the amount of radiation emerging from the
opposite side (see Figure 3.1) of the object (or part) can be detected by means
of a radiographic film, variations in this amount of emerging radiation create
differing degrees of radiographic film blackening, which in turn is related to
the thickness of the object (or part).