6-22 shows that, for a given subject, a doubling of kilovoltage increases transmitted radiation 15 to 30 times. This
example shows the disproportionate effect a small kilovoltage change can have upon a particular inspection.
Figure 6-21. Effect of Kilovoltage on Transmitted Radiation Output.
a. 38 kVp, 5 minutes
b. 80 kVp, 5 seconds
Figure 6-22. Radiographs of Honeycomb Showing Effect of Kilovoltage on Contrast.
If industrial radiographic applications were to use monochromatic radiation and if there was no scattering to be
considered, the radiation absorption could be mathematically calculated with high precision using the classical
attenuation equation. However, in normal applications, it is not possible to calculate the right kilovoltage to be used for
a particular inspection because this optimum condition does not exist. The best initial approach is to use past
experience. Table 6-12 indicates approximate radiation energies compatible with various subjects.