Liquid Penetrant Testing Level 2 (PT-2) Practice Exam

The efficiency of fluorescent dyes in the liquid penetrant testing process is enhanced under black light of which wavelength?

1. 2.0 × 10-7m (2000 Å)

2. 2.5 × 10-7m (2500 Å)

3. 3.25 × 10-7m (3250 Å)

4. 3.65 × 10-7m (3650 Å)

The correct answer is: 3.65 × 10-7m (3650 Å)

The efficiency of fluorescent dyes used in liquid penetrant testing is indeed enhanced under specific wavelengths of black light. Fluorescent dyes are designed to absorb certain wavelengths of light and then re-emit light at longer wavelengths, which is critical for detecting defects in materials. In this case, the correct choice corresponds to a wavelength of 3.65 × 10^-7 meters, or 3650 Å. This wavelength is effective because it falls within the ultraviolet spectrum that is optimal for activating fluorescent dyes used in penetrant testing. Under this wavelength, the dyes can achieve maximum fluorescence, making it easier for inspectors to identify defects. The other wavelengths presented, such as 2000 Å, 2500 Å, and 3250 Å, may not provide the same level of efficiency because they are either too short or insufficiently effective at exciting the fluorescent materials used in the process. The choice of 3650 Å is based on extensive testing and optimization to ensure that the detection process is reliable and accurate under typical viewing conditions in fluorescent penetrant testing.