The inspector controls the intensity of the UV light and the thickness of the penetrant dye. Which of the following statements best reflects this control?

• A. The thickness of the penetrant dye
• B. The color of the penetrant
• C. The intensity of the UV light and the thickness of the penetrant dye
• D. The concentration of the dye on the surface

Answer: (C)

In this inspection method, whether a flaw shows up depends on how bright the fluorescent indication is and how much penetrant remains in the surface openings. The inspector actively adjusts two things to control that visibility: the intensity of the UV light and the thickness of the penetrant film on the surface. If the penetrant layer is too thick, background glow can mask small indications; if it’s too thin, there may not be enough penetrant to reveal cracks. Likewise, if the UV light is too dim, the fluorescence may be hard to see; if it’s too bright, it can wash out markings or create glare that obscures flaws. The color of the penetrant is determined by the product itself, not something routinely tuned during inspection, and the concentration on the surface is effectively what the film thickness describes. Thus the best reflection of the inspector’s control is the combination of UV light intensity and penetrant film thickness.