Which of the following is important when using eyewear with diffraction filters?

When using eyewear with diffraction filters, the narrow angle of incidence is particularly important because it directly affects the performance of the filter in protecting the eyes from harmful laser radiation. Eyewear designed for use with diffraction filters is typically optimized for specific angles. If the angle of incidence of the incoming laser light strays too far from this optimal range, the effectiveness of the eyewear can be significantly reduced, potentially allowing harmful radiation to reach the eyes.

Each diffraction filter is designed to diffract light that hits it at particular angles, and therefore, if the light enters at a broader angle, the filter may not function correctly, failing to block or redirect the laser light effectively. This makes understanding and adhering to the guidance on angles of incidence essential in situations where lasers are in use, as it ensures maximum protection and safety for the wearer.