Which class of lasers used for alignment is visible?

The correct answer is Class 2 lasers. Class 2 lasers emit visible light, typically in the range of 400 to 700 nanometers, which is the spectrum visible to the human eye. This makes them particularly useful for alignment tasks, as operators can easily see the beam and ensure that the alignment is accurate. The visible nature of Class 2 lasers helps in direct observation and adjustments during the alignment process, enhancing user safety since these lasers can cause temporary visual impairment if viewed directly for extended periods, but generally do not pose a significant risk.

In contrast, other classes of lasers, such as Class 1, which are considered safe under all conditions of normal use, do not emit visible light that could be utilized for alignment tasks. Class 3 lasers can be subdivided into Class 3R and Class 3B; while some Class 3 lasers can be visible, they often pose a higher risk of injury and require greater caution when used for alignment. Class 4 lasers are much more powerful and can be harmful to the eyes and skin, making them unsuitable for typical alignment applications where visibility and safety are prevalent concerns. Thus, Class 2 lasers strike a balance of visibility and safety suitable for alignment in millwright applications.