Liquid Penetrant Testing Level 1 (PT-1) Practice Exam

What type of lighting is typically used for fluorescent penetrant testing?

1. Daylight

2. Infrared

3. Ultraviolet

4. Standard white light

The correct answer is: Ultraviolet

Fluorescent penetrant testing relies on ultraviolet (UV) light to facilitate the detection of surface discontinuities in a material. When the penetrant, which is applied to the surface being inspected, enters cracks or voids, it is designed to fluoresce when exposed to UV light. This fluorescence makes the indications of surface defects much more visible against a dark background. The use of UV light is crucial because it enhances the contrast of the fluorescent penetrant against the surface, allowing for greater sensitivity in detecting very fine defects. In contrast, other lighting types, such as daylight or standard white light, do not provide the necessary contrast and sensitivity because they cannot adequately emphasize the fluorescing properties of the penetrant. Infrared lighting, on the other hand, works in a different spectrum that does not interact with fluorescent materials, making it unsuitable for this testing method. Thus, ultraviolet lighting is essential for effective fluorescent penetrant testing.