Why is black light equipment necessary when using fluorescent penetrants?

Using black light equipment is essential when employing fluorescent penetrants because these penetrants are designed to fluoresce under specific wavelengths of ultraviolet (UV) light, typically emitted by black lights. When the penetrant is applied to a surface, it seeps into any defects or imperfections. Once exposed to black light, the fluorescent penetrant becomes visible, glowing brightly against the surface background, which helps in identifying cracks or other issues. This fluorescent effect is pivotal in non-destructive testing, as it allows for an effective visual inspection that highlights flaws that might not be easily seen under standard lighting conditions.

The other options relate to different considerations in the inspection process but do not capture the primary role of black light in the effectiveness of fluorescent penetrants.